Method for producing an optical element by processing an optically active material, and optical element

Abstract

Method for manufacturing an optical element by processing an optically reactive material

Description

[0001] The invention relates to a method for producing an optical element by processing an optically reactive material, as well as an optical element produced by the method, a corresponding device and an optical element produced according to the method. background

[0002] Subtractive manufacturing processes for optical elements, such as milling, grinding, and polishing materials, are time-consuming and expensive. Other shaping processes, like precision glass pressing or injection molding of polymer materials, involve increased manufacturing tolerances and high initial costs for mold production. Additive manufacturing processes, on the other hand, offer the advantage of producing any three-dimensional object in a material-, time-, and cost-efficient manner.

[0003] Optical elements can be additively manufactured using various processes, such as stereolithography or digital light processing. However, both processes inherently require layer-by-layer construction. Furthermore, only low-viscosity materials can be used, as these must flow freely. With layer thicknesses between 10 µm and 100 µm, this always results in a loss of geometric accuracy for curved surfaces. Additionally, the layer-by-layer construction leads to density inhomogeneities and thus to inhomogeneities in the optical and mechanical properties within the component. The layer-by-layer construction of these processes also always involves long waiting times in the individual process steps, resulting in long overall production times. Finally, overhanging structural elements must be supported with structures in the aforementioned processes.The construction of these support structures is not only time-consuming, material-intensive, and therefore costly. Furthermore, the contact points between these support structures and the component further reduce the surface quality of the manufactured parts. While the surface finish can be improved through post-processing steps such as polishing or coating, this also results in a loss of geometric accuracy and is an additional process step that is both time-consuming and costly.

[0004] In Continuous Liquid Interphase Production (CLIP, Nature Materials, 5, 365-369 (2006)), the build chamber is irradiated from below through an oxygen-permeable membrane, creating a chemical inhibition zone that enables the continuous build-up of isotropic objects. While this method is significantly faster than conventional stereolithography, it is still dependent on the flow behavior of the photoresins, which precludes the use of highly viscous materials suitable for producing polymers with high mechanical strength. Furthermore, this method requires support structures, which introduce the aforementioned disadvantages. There are also chemical limitations regarding the resin, as oxygen inhibition does not function with cationic polymerization or thiol-ene resins. Finally, some additives, such as bases, cannot be used because they counteract oxygen inhibition.

[0005] Document WO2014 / 108364A1 discloses a multi-jetting process in which a layer of small liquid photoresist droplets is precisely deposited onto a surface and subsequently cured by UV irradiation. By skillfully controlling the wetting properties, the natural curvature of the individual droplet surfaces can be utilized to achieve very high surface qualities, even though the process is still layer-by-layer. However, due to process limitations, low-viscosity materials are also used, and these methods can only create one free-form optical surface at a time, which is also subject to restrictions regarding printable angles and other geometric limitations.

[0006] Document DE 10 2020 108 375 B3 discloses a method for manufacturing an intraocular lens comprising the following steps: providing a container transparent to electromagnetic radiation in which a liquid is arranged that can be cured by electromagnetic radiation; irradiating the liquid with a set of images formed by the electromagnetic radiation, each showing an intraocular lens, wherein each of the images in the set is irradiated into the liquid at a different angle of incidence with respect to a reference plane passing through the liquid, thereby curing the liquid and the cured liquid forming the intraocular lens. The method is limited in that strongly anisotropic structures or sharp edges cannot be formed, thus restricting the freedom of design.

[0007] For the production of optical elements, starting materials can be optically processed by shining light of one or more wavelengths onto them in order to alter at least one material property. For example, it is known to harden a starting material using such optical processing.

[0008] Document US 4,041,476 describes a method and apparatus for producing a three-dimensional body from a starting material by shining light beams of different wavelengths onto the starting material, where they overlap at points.

[0009] Polymerization is a reaction used to produce plastics. Photopolymerization is a form of optical processing of a starting material. is, willThe reaction is triggered by irradiating the polymerizable starting material with light. Such polymerizable starting materials are also called photopolymers. These are polymers that change their material properties when exposed to light. The light irradiation causes structural changes, such as the photochemical curing of the material through cross-linking. Photopolymerization is used, for example, in 3D printing to produce three-dimensional objects from the cured material by irradiating the polymerizable starting material with light.

[0010] The starting material itself can be transparent to the incident light and therefore insensitive. Photoinitiator molecules are added, which absorb the light and initiate the curing of the starting material. For processing the starting material in its unaltered (free) volume, it is necessary to address a freely chosen point in three-dimensional space. One possibility is the use of special photoinitiators, also known as dual-color photoinitiators (WO 2020 / 245456 A1 and WO 2021 / 089090 A1). These are preferably or exclusively excited by the absorption of photons of two different wavelengths or two different, non-overlapping wavelength ranges. Dual-color photoinitiators can be generated in various ways. In one variant, molecules without light exposure exhibit a ground / normal state (A).In this state, the molecule has an absorption band for one wavelength λ 1 and the lowest possible absorption at another wavelength λ 2 .

[0011] The molecules can then assume a pre-activated or excited intermediate state (B). The pre-activated or excited intermediate state is generated by absorption of light of wavelength λ₁ from the ground state A. In intermediate state B, the photoinitiator molecules exhibit an absorption band for wavelength λ₂. The absorption band for wavelength λ₁ disappears. Alternatively, the absorption band for wavelength λ₁ remains. This creates an undesired, competing transition channel to state C. In the absence of light, the photoinitiator molecule returns to state A. Alternatively, after excitation with light of a third wavelength λ₃, the photoinitiator molecule returns to state A. This allows for targeted inhibition of the initiator in state B.

[0012] The active state C of the molecules is generated by absorption of wavelength λ₂ from B. State C initiates a chemical and / or physical modification of the molecule's immediate environment. A reverse reaction to B is not intended, but possible. Summary

[0013] The object of the invention is to provide a method for producing an optical element by processing an optically reactive material, with which a starting material can be optically processed in a multidimensional manner in an efficient manner.

[0014] The solution comprises a method for manufacturing an optical element by processing an optically reactive material, as well as an optical element according to the independent claims. Embodiments are the subject of dependent subclaims.

[0015] According to one aspect, a method for producing an optical element by processing an optically reactive material is provided, comprising the following: providing a starting material that is optically reactive and fills a working volume; optically processing the starting material in the working volume by irradiating it with light of a first wavelength and light of a second wavelength, which differs from the first wavelength, wherein at least one material property of the starting material is modified by the optical processing. The optical processing includes the following: irradiating a first layer subvolume of the working volume filled with the starting material with light of the first wavelength; irradiating the first layer subvolume of the working volume with light of the second wavelength, wherein the light of the second wavelength is projected into the working volume;Irradiating a second layer volume of the working volume filled with the starting material, which differs from the first layer volume, with light of the first wavelength; irradiating the second layer volume of the working volume with light of the second wavelength, whereby the light of the second wavelength is projected into the working volume; and repeating the preceding steps for layer-by-layer optical processing of the starting material in the working volume until a volume of the starting material to be processed, which wholly or partially encompasses the working volume, has been optically processed, and a green compact has been formed from the starting material; and further processing of the green compact so that an optical element is formed from the green compact, at least partially, and in particular completely.

[0016] In particular, the method comprises the following: providing a starting material that is optically reactive and fills a working volume; optically processing the starting material in the working volume by irradiating it with light of a first wavelength and light of a second wavelength that differs from the first wavelength, wherein the light of the first wavelength and the light of the second wavelength are provided by an illumination device, and wherein at least one material property of the starting material is modified by means of the optical processing. The optical processing comprises the following: irradiating a first partial volume of the working volume filled with the starting material with the light of the first wavelength;Irradiation of the first layer volume of the working volume with light of a second wavelength, wherein the light of a second wavelength is projected into the working volume, covering only the first layer volume completely or partially, by means of a projection device; Irradiation of a second layer volume of the working volume filled with the starting material, with the starting material, which is different from the first layer volume, with light of a first wavelength; Irradiation of the second layer volume of the working volume with light of a second wavelength, wherein the light of a second wavelength is projected into the working volume, covering only the second layer volume completely or partially, by means of the projection device;and repeating the preceding steps for layer-by-layer optical processing of the starting material in the working volume until a volume of the starting material to be processed, which wholly or partially encompasses the working volume, is optically processed and a green body (blank) is formed from the starting material; and further processing of the green body so that an optical element (at least partially, in particular completely) is formed from the green body.

[0017] According to another aspect, an optical element is created, which is manufactured using the process.

[0018] This method enables the efficient production of an optical element. The starting material, which is placed in the working volume and fills it completely before the application of first- and second-wavelength light, can be optically processed multidimensionally or spatially within the working volume. This process involves illuminating at least one material property of the starting material with first- and second-wavelength light, or optionally with light of one or more additional wavelengths. Subsequent processing (post-processing) then yields an optical element. This method can provide a volumetric 3D printing process, which can be operated continuously and thus enables the production of isotropic objects.

[0019] The invention is based on the surprising finding that volumetric 3D printing processes, which involve irradiating corresponding layer volumes with light of a first and a second wavelength, are ideally suited for the production of optical elements. In particular, optical elements with excellent properties and high quality can be efficiently produced using corresponding volumetric 3D printing processes, which involve irradiating corresponding layer volumes with light of a first and a second wavelength. The invention thus breaks with the previously prevailing view that optical elements, especially larger optical elements, with desired properties cannot be produced using volumetric 3D printing processes; in particular, investigations have shown that, for example,CT-based axial lithography (computed axial lithography), or CAL for short, is unsuitable, particularly because this method is only conditionally suitable for the production of micro-optics or leads to component surfaces with artifacts that preclude the use of the printed component as an optical element. In other words, the inventors were able to determine that, surprisingly, it is indeed possible to use certain volumetric 3D printing processes, namely, in particular, volumetric 3D printing processes that involve irradiating corresponding layer volumes with two different wavelengths, for the production of optical elements, especially optical elements made of polymer materials or plastics.

[0020] Furthermore, a device for processing an optically reactive material is disclosed, which may include: a working volume which is configured to receive a starting material which is optically reactive and partially or completely fills the working volume; a lighting device which is configured to provide light of a first wavelength and light of a second wavelength for illuminating the working volume containing the starting material.The illumination device can be configured to optically process the starting material in the working volume as follows: irradiating a first layer subvolume of the working volume, which is partially or completely filled with the starting material, with light of the first wavelength; irradiating the first layer subvolume of the working volume with light of the second wavelength; irradiating a second layer subvolume of the working volume, which differs from the first layer subvolume, with light of the first wavelength; irradiating the second layer subvolume of the working volume with light of the second wavelength; and repeating the preceding steps for layer-by-layer optical processing of the starting material in the working volume until a volume of the starting material to be processed, which wholly or partially encompasses the working volume, is optically processed, in particular forming a corresponding green compact.

[0021] In particular, the device may comprise the following: a working volume configured to receive an optically reactive starting material that fills the working volume; an illumination device configured to provide light of a first wavelength and light of a second wavelength for illumination onto the working volume containing the starting material; and a projection device configured to project the light of the second wavelength, when illuminated onto the working volume filled with the starting material, into a sub-volume of the working volume, capturing only that sub-volume, either wholly or partially. The illumination device and the projection device may further be configured to optically process the starting material in the working volume as follows: illuminating a first sub-volume of the working volume filled with the starting material with light of the first wavelength;Irradiation of the first layer volume of the working volume with light of a second wavelength, wherein the light of a second wavelength is projected into the working volume, covering only the first layer volume completely or partially, by means of a projection device; Irradiation of a second layer volume of the working volume filled with the starting material, with the starting material, which is different from the first layer volume, with light of a first wavelength; Irradiation of the second layer volume of the working volume with light of a second wavelength, wherein the light of a second wavelength is projected into the working volume, covering only the second layer volume completely or partially, by means of the projection device;and repeating the preceding steps for layer-by-layer optical processing of the starting material in the working volume until a volume of the starting material to be processed, which encompasses the working volume completely or partially, is optically processed and a green body is formed from the starting material. An optical element (at least partially, in particular completely) can be formed from the green body through further processing.

[0022] The lighting device of the apparatus, also referred to herein as the irradiation device, may be configured to generate a light section in the working volume or may include a light section generation device for generating a light section in the working volume.

[0023] The illumination device can, for example, comprise at least one of the following elements: a Powell lens, a cylindrical lens, in particular a plano-oconvex cylindrical lens, or a polygonal mirror or a galvo scanner. Alternatively or additionally, the illumination device can, for example, comprise: a laser or an LED or a thermal light source. Alternatively or additionally, the illumination device can, for example, comprise: a mirror or a light deflection device, which are configured to reflect the light exiting the working volume back into the working volume in the opposite direction.

[0024] The lighting system can be configured to allow earlier processing of layers that are further away from a source of light of the second wavelength.

[0025] Sub-volumes of the working volume are irradiated successively with the first and second wavelengths to trigger an optically initiated reaction in the starting material. The sub-volumes that are optically processed successively contain and are filled with portions of the starting material that is introduced into the working volume before the start of the manufacturing process (optical processing). Unlike known methods, optical processing does not involve the layer-by-layer application of the starting material followed by layer-by-layer optical processing (of the layer just applied) after each layer application.

[0026] Depending on which portion of the layer within the working volume (previously filled with the starting material) is irradiated with the first wavelength, the projection of the second wavelength light, or the irradiation with the second wavelength light, occurs precisely within this portion of the layer currently irradiated with the first wavelength, using the projection device. The projection device maps the second wavelength light onto the desired portion of the layer. It can project the second wavelength light onto the projection plane or volume, corresponding to an image of at least two dimensions, located within the portion of the layer irradiated with the first wavelength light. In this way, for example, a three-dimensional object can be produced layer by layer within the starting material.

[0027] Further processing of the green compact can include at least one of the following steps: removing the green compact from the starting material; treating (especially washing) the green compact with a solvent and / or a (treatment) monomer; and drying the (washed) green compact. The green compact can be isotropically formed.

[0028] Alternatively, the further processing steps can be carried out in the starting material (without removing the blank).

[0029] The solvent and / or (treatment) monomer can contain a photoinitiator and / or a thermal initiator, preferably reacting at only one wavelength (or wavelength range). This allows for more efficient post-curing. The photoinitiator and / or thermal initiator can be designed to be incorporated into the surface of the green compact. In particular, a photoinitiator and / or thermal initiator can be dissolved in the solvent and / or the (treatment) monomer. Drying can be achieved, for example, by supplying a gas stream (preferably an air or nitrogen stream) and / or by supplying heat (preferably at a temperature of at least 20 °C). Photoinitiators are described, for example, in Fouassier / Lalevée, Photoinitiators, Wiley-VCH (2021).

[0030] Especially for highly viscous starting materials, washing can result in smoother surfaces of the green body by appropriately selecting the solvent or (treatment) monomer, time, temperature and movement.

[0031] In addition or alternatively, further processing of the green body can include at least one of the following steps: photochemical post-curing of the green body, tempering of the green body (this typically corresponds to thermal post-curing of the green body), grinding of the green body, polishing of the green body and coating of the green body (for example with an anti-reflective coating).

[0032] Coating the green compact can be carried out using one or more chemical and / or physical coating processes and serves in particular to improve the surface properties of the green compact and thus of the optical element. Specifically, the roughness, scratch resistance, and / or reflection properties can be improved by applying at least one coating. For all embodiments, an applied coating can therefore have a lower refractive index than the (actual) optical element (e.g., through an anti-reflective coating) and / or increase the surface hardness of the optical element (e.g., through an anti-scratch coating).

[0033] Suitable coating processes can include, for example, spray coating, dip coating, spin coating, sol-gel coating, or vapor deposition. Following any coating process, further curing can be carried out, which can again be done, for example, photochemically or thermally.

[0034] A coating material to be applied by means of a suitable coating process can be, for example, a solid, a paste, a liquid or lacquer, or a gas. Thus, a coating material can be applied to the green compact, for example, as a powder, a paste, a liquid or lacquer, or as a gas or from a gas phase.

[0035] A coating can also be applied using the uncured starting material itself or another organic polymer or an inorganic-organic hybrid material, which typically requires further curing, which in turn can be done, for example, photochemically or thermally.

[0036] The surface of the green body or optical element can be chemically and / or physically prepared, i.e., activated, before the coating is applied to improve adhesion. Such preparation or activation can be achieved using a plasma, particularly an oxygen plasma. Alternatively or additionally, adhesion promoters can be used to improve the bonding of the coating to the green body or optical element.

[0037] Photochemical post-curing can be achieved by isotropic irradiation of the green compact (uniform irradiation from all sides with light). Tempering or thermal post-curing can be achieved by applying heat at temperatures of at least 50 °C, particularly for a duration of at least 15 minutes, or by exposing the green compact to temperatures of at least 50 °C, particularly for a duration of at least 15 minutes.

[0038] With the aid of a control device connected to one or more light sources or irradiation devices for providing the light of the first and the light of the second wavelength, and optionally a projection device, which can generally form part of an irradiation device, it can be determined whether the first or the second layer volume (of the starting material in the working volume) is irradiated, and the projection device can be controlled accordingly to project the light of the second wavelength into the first and / or the second layer volume. InThe control unit receives data defining the current or instantaneous position of the layer volume being irradiated with light of the first wavelength. Based on this, the projection unit is controlled so that the projection generated by the projection unit is placed in a projection plane or volume within this currently irradiated layer volume. In this way, the layer volumes of the starting material are processed layer by layer. The external shape of the projection can vary for different layer volumes, particularly depending on the three-dimensional object being produced in the starting material using optical processing.

[0039] In one embodiment, it may be provided to detect a current or instantaneous position of the layer subvolume, which is irradiated with the light of the first wavelength, in the working volume by means of a measuring device, which then sends measurement signals indicating the position to the control device.

[0040] The light of the first wavelength and the light of the second wavelength can be simultaneously illuminated into the first or the second layer volume, at least for a period of temporal overlap. In this embodiment, the area covered by the layer volume and the projection of the projection device is illuminated with both light of the first wavelength and light of the second wavelength, at least for the period of temporal overlap.

[0041] The first and second layer subvolumes can form adjacent layer subvolumes of the starting material within the working volume.

[0042] It may be provided that the first and second layer sub-volumes are formed according to one of the following configurations of sub-volumes: overlapping at the edges, abutting at the edges, and spaced apart from each other at the edges.

[0043] Light of the first wavelength can be directed onto the starting material in the working volume along a first direction of incidence, and light of the second wavelength can be directed along a second direction of incidence, which runs perpendicular to the first direction of incidence. In one embodiment, the first and second directions of incidence can, for example, form an angle of approximately 90°. Other angles in the range of approximately 30° to 90° between the optical axes of the directions of incidence can be provided.

[0044] Light of the first wavelength and / or light of the second wavelength can be applied as pulsed light. The light pulses of the first and second wavelengths can be applied simultaneously or sequentially at predetermined intervals to the currently processed layer volume. The light pulses for the two wavelengths can be provided with the same or different pulse widths. Alternatively, light of the first wavelength or light of the second wavelength can be applied as continuous light.

[0045] The starting material can be processed by optical means according to at least one processing method from the following group: curing, hardening, gelling, and liquefaction. In this or other embodiments, the starting material can be solid, liquid, or pasty.

[0046] In one embodiment, it may be provided that the starting material is made to glow due to optical processing with first and second wavelength light, in particular due to fluorescence or phosphorescence.

[0047] To irradiate the first layer volume and the second layer volume with light of the first wavelength, a layered beam area of ​​a first light source, which provides the light of the first wavelength, can be displaced relative to the working volume. In this embodiment, the layered beam area for the light of the first wavelength is shifted relative to the working volume during the optical processing of the starting material, so that the beam area essentially moves or sweeps across the working volume. The relative movement between the working volume and the beam area can be realized in various ways. A displacement of the working volume and / or the first light source can be provided. Alternatively or additionally, the working volume and the first light source can be fixed relative to each other during the complete processing of the starting material.With the help of a light deflection device, the beam area for the light of the first wavelength is then moved from the first light source over the working volume containing the starting material.

[0048] It may be possible to observe the optical processing of the starting material using one or more light detectors, for example, a camera and / or a photodetector. This allows the processes during processing (optical treatment) to be investigated by measuring, for example, the transmitted light, whether light from the excitation of the light section and / or light from the projector. The light section generator and / or the projector can emit additional wavelengths of light that differ from the excitation wavelengths and serve solely to observe changes in the material properties of the starting material, for example, the ongoing polymerization.

[0049] Optical processing can trigger polychrome multiphoton polymerization ("xolography") in the starting material, which alters at least one material property of the starting material. In an exemplary embodiment, the starting material can be a transparent organic polymer and / or an inorganic / organic polymer composite, which preferably cures by optical processing.In an exemplary embodiment, the starting material can comprise one or more of the following components: oligomer (e.g., acrylate, methacrylate, epoxy, vinyl, allyl, organopolysiloxanes, terminally functionalized polysiloxanes), functionalized and non-functionalized nanoparticles, monomer (e.g., acrylate, methacrylate, epoxy, vinyl, allyl), crosslinker (e.g., multifunctional monomers, multifunctional thiols), dual-color photoinitiator, co-initiator, inhibitor, sensitizer, defoamer, post-processing additive (e.g., additional photoinitiator and / or thermal initiator), solvent, additive, in particular an additive for rheology control (rheology modifier), especially of the starting material, additive for reducing surface tension, especially of the starting material, additive for influencing optical properties, for example, to adjust or increase transparency.Adjustment of the refractive index, in particular of the starting material or the optical element.

[0050] The dual-color photoinitiator can react to light of two different wavelengths and in particular lead to local polymerization, preferably resulting in selective curing. In In one embodiment, a transparent container filled with monomer and dual-color photoinitiator can be illuminated from one side with a laser line, creating a light section. A video can then be projected onto this light section. By moving the container, a hardened object can be created that appears to float freely.

[0051] The method can (preferably during video projection) include pixel shifting, thus preferably achieving automatic edge smoothing. Furthermore, software-based layering of the object with layer thicknesses <=1 µm at a constant printing speed can be provided, preferably resulting in a high resolution of the optical element.

[0052] The starting material can have a viscosity of 10 2< mPa·s to 10 7< mPa·s, preferably of 3 · 10 3< to 10 6< mPa·s, particularly preferably of 10 3< to 10 5< mPa·s, most preferably of 10 4< to 9 · 10 4< mPa·s.

[0053] The starting material can be a monomer mixture and / or an oligomer mixture, preferably with a suitable viscosity. The monomer mixture and / or oligomer mixture can preferably be transparent. The monomer mixture and / or oligomer mixture can stabilize the green compact and / or a cured object, thereby eliminating the need for support structures and providing complete structural freedom. The cured object can be formed free-floating within the monomer mixture and / or oligomer mixture.

[0054] In particular, the cured object, i.e., the green compact, can form free-floating within the monomer mixture and / or oligomer mixture, i.e., generally within the starting material, if the monomer mixture or the oligomer mixture, generally the starting material, has a sufficiently high viscosity to support the cured object. Alternatively or additionally, the cured object can form free-floating within the monomer mixture and / or oligomer mixture, generally within the starting material, if the monomer mixture or the oligomer mixture, generally the starting material, exhibits non-Newtonian flow properties, i.e., shear-thinning or shear-liquefying flow properties, and / or has a yield strength that is greater than the static shear stress exerted by the object. The yield strength of the starting material can, for example,by rotational rheometry (plate-plate rheometer) under quasi-static loading via "creep test" or driving a slow shear stress ramp.

[0055] A corresponding yield strength of the starting material, which is greater than the static shear stress exerted by the object, is typically greater than or equal to 0.1 Pa, in particular 0.2 Pa, further in particular 0.3 Pa, further in particular 0.4 Pa, further in particular 0.5 Pa, further in particular 0.6 Pa, further in particular 0.75 Pa, further in particular 1 Pa. A corresponding yield strength of the starting material can therefore be, in particular, at least 0.1 Pa per cm³ of the working volume. For a working volume of 1 cm³, the yield strength of the starting material can therefore be at least 0.1 Pa. For a working volume of 2 cm³, the yield strength of the starting material can therefore be at least 0.2 Pa.

[0056] The static shear stress exerted by the object depends in particular on its geometry and size and can therefore be less than or greater than 0.5 Pa, depending on these factors. To achieve the desired rheological properties of the monomer mixture or oligomer mixture, or generally the starting material, it may be advantageous to allow the monomer mixture or oligomer mixture, or generally the starting material, to settle before optical processing, i.e., before printing. The starting material can thus be allowed to settle for a certain period of time, particularly after being placed in a container defining the working volume, specifically for at least one hour, at least six hours, at least twelve hours, at least eighteen hours, or at least twenty hours.

[0057] Alternatively or additionally, the yield strength of the starting material can be adjusted by adding oligomers and polymers with non-Newtonian flow properties and / or by adding additives (rheology modifiers). Examples of oligomers with non-Newtonian flow properties include (but are not limited to): 1) linear polymers with medium and / or high molecular weight, e.g., PMMA, PS, PC, PIM; 2) cellulose and cellulose esters; 3) polyacrylic acid and polyacrylic acid-polyacrylic ester copolymers; 4) polyacrylamides; 5) polyethylene oxide; and 6) polyurethanes. Examples of rheology modifiers include (but are not limited to): 1) inorganic (nano)particles, e.g.,Pyrogenic silica, natural and synthetic clay minerals, layered silicates, glass, 2) Organically modified inorganic (nano)particles, 3) organic molecules, oligomers and polymers (urea derivatives, polysaccharides, polyacrylic acids, polyacrylates, polyamides, polyethers, polyurethanes, polyurea derivatives) and 4) urea-modified polyacrylates, polyethers, polyamides and polyurethanes. Examples of commercial organic rheology modifiers that can be used include, but are not limited to: RHEOBYK 410, RHEOBYK 420, RHEOBYK 430, RHEOBYK 440, BYK-LP R21675, RHEOBYK 7410CA, RHEOBYK 7420CA, RHEOBYK 7420ET (all available from BYK-Chemie GmbH, 46486 Wesel (DE)), JL-106 (available from Bomar Chem, 51 Greenwoods Rd, Torrington, CT 06790).

[0058] For any rheology modifier, it is preferably selected or used in such a way, e.g. with regard to its chemical and / or physical properties, concentration, etc., that it does not or hardly leads to a clouding of the starting material and / or the cured material after optical processing.

[0059] It should be noted generally that the starting material, particularly in a wavelength range between 370 and 800 nm, further particularly between 400 and 800 nm, further particularly between 450 and 800 nm, further particularly at 600 nm, typically exhibits a transmission of at least 10%, in particular at least 20%, further in particular at least 30%, further in particular at least 40%, further in particular at least 50%, further in particular at least 60%, further in particular at least 70%, further in particular at least 80%, further in particular at least 90%, further in particular at least 95%, further in particular at least 99% in the region of the incident light of the first wavelength and / or in the region of the incident light of the second wavelength. The optical transmission refers to an optical path length of 10 mm according to the Lambert-Beer law.

[0060] It should also be noted generally that the optical element, particularly in a wavelength range between 370 and 800 nm, further particularly between 400 and 800 nm, further particularly between 450 and 800 nm, further particularly at 600 nm, typically exhibits a transmission of at least 10%, particularly at least 20%, further particularly at least 30%, further particularly at least 40%, further particularly at least 50%, further particularly at least 60%, further particularly at least 70%, further particularly at least 80%, further particularly at least 90%, further particularly at least 95%, further particularly at least 99% in the region of the incident light of the first wavelength and / or in the region of the incident light of the second wavelength. The optical transmission refers to an optical path length of 10 mm according to the Lambert-Beer law.

[0061] The terms "transparency" and "transmission" can be understood as equivalent in this context.

[0062] In general, the starting material can exhibit non-Newtonian rheological behavior. Such rheological behavior can facilitate the fabrication of an object by exposure to at least two different wavelengths, where the object remains in a fixed position within the working volume or is not moved, or only minimally moved, within the working volume during formation. Such minimal movement can refer to the displacement of the object during formation within the working volume that is acceptable for precise fabrication. Such rheological behavior can also facilitate the separation of the partially fabricated object from the working volume when mechanical stresses are applied. The viscosity or apparent viscosity of the non-Newtonian starting material can decrease to a lower value (e.g.,The constant shear viscosity decreases compared to the static value (e.g., zero-shear viscosity or yield stress), allowing the starting material to flow more easily and separate from the object. Examples of such non-Newtonian rheological behavior include pseudoplastic behavior, Bingham behavior, dilatant (shear-thickening) behavior, and shear-thinning (thinning) behavior.

[0063] A non-Newtonian rheological behavior can be imparted to a starting material, for example, by adding one or more reactive components (e.g.,Urethane acrylate oligomers, urethane methacrylate oligomers, acrylated or methacrylated polyurethanes, acrylated or methacrylated polyurethane ureas, acrylated or methacrylated polyesters, acrylated or methacrylated polyamides, acrylate or methacrylate functional block copolymers, alkenyl or alkynyl functional urea imidomers, alkenyl or alkynyl functional polyurethanes, alkenyl or alkynyl functional polyurethane ureas, alkenyl or alkynyl functional polyesters, alkenyl or alkynyl functional polyamides, alkenyl or alkynyl functional block copolymers, thiol-functional urea imidomers, thiol-functional polyurethanes, thiol-functional polyurethane ureas, thiol-functional polyesters, thiol-functional polyamides, thiol-functional block copolymers) in the photocurable starting material component and / or by further addition of one or more non-reactive additives (e.g.(but not limited to, one or more thixotropes and / or rheology modifiers) to the starting material. The selection of one or more reactive components and their amounts for addition to a photocurable starting material component to impart non-Newtonian rheological behavior to the starting material can, in principle, be freely chosen in order to obtain specific rheological properties of the starting material.

[0064] The starting material can, for example, have a viscosity or a constant shear viscosity that is less than 30,000 mPas, less than 20,000 mPas, less than 10,000 mPas, less than 5,000 mPas or less than 1,000 mPas. (Constant shear viscosity refers to the plateau value of the viscosity reached at unidirectional constant shear, e.g., the viscosity value after the thixotropic network has broken down. Preferred constant shear viscosities are less than 30,000 mPas, more preferably less than 10,000 mPas, and most preferably less than 1,000 mPas. The viscosity at constant shear can be measured at ambient temperature (e.g., room temperature), printing temperature, or another temperature (e.g., increased or decreased). Measurement at printing temperature can be advantageous in determining the suitability of a starting material for printing.)

[0065] The constant shear viscosity can be measured, for example, under continuous shearing at a constant rate, e.g., at shear rates from approximately 0.00001 s⁻¹ to approximately 1000 s⁻¹.

[0066] As mentioned, the starting material can contain at least one additive. Examples of additives include, as mentioned, a filler, a thixotrope or rheology modifier, a defoamer, a stabilizer, an oxygen scavenger, a non-reactive solvent or diluent, and a dye. Each additive can be a single additive or a mixture of several additives. A thixotrope, for example, can be a single thixotrope or a mixture of two or more thixotropes.

[0067] The additives can preferably be selected in such a way that they do not react in an undesirable way with other components or additives that are or may be contained in the starting material.

[0068] As mentioned, an additive can be a filler or at least include one. A filler can be present in an amount ranging from more than 0 to approximately 90 wt.%, the amount typically being determined by the purpose of the filler and the desired end-use properties of the object to be manufactured. Advantageously, the fillers can be selected to preserve the optical properties, particularly the transparency or transmission, of the starting material, for example, by selecting the particle size of the filler to be significantly smaller than the excitation wavelengths, or by matching the refractive indices of the filler and the starting material acting as the matrix to prevent or at least reduce undesired scattering effects. Fillers can be used, in particular, to modify one or more properties of the starting material or the object, for example, by...Regarding stiffness, strength, toughness, impact strength, creep resistance, fatigue strength, mechanical energy return, mechanical loss tangent, glass transition temperature, thermal decomposition temperature, thermal conductivity, thermal stability, moisture absorption, electrical conductivity, static dissipation, dielectric constant and loss tangent, density, refractive index, optical dispersion, opacity to ionizing radiation, and resistance to ionizing radiation. Fillers can, as indicated, also be used to modify the properties of the starting material or object, e.g., rheological properties such as viscosity and thixotropy, and optical properties such as the refractive index.Examples of fillers include silicon dioxide, aluminum oxide, zirconium dioxide, silicate glasses such as soda-lime glass, borosilicate glass, sodium silicate glass, lead glass, aluminosilicate glass, barium glass, thorium glass, glass ceramics, chalcogenide glasses, glass microspheres and microbubbles; nanotones such as laponite, montmorillonite, bentonite, kaolinite, hectorite and halloysite; calcium phosphate minerals such as hydroxyapatite, mineral fillers such as chalk, rock dust, slag dust, fly ash, hydraulic cement, loess, limestone, kaolin, talc and wollastonite. Examples of particle size ranges are less than 10 micrometers, less than 1 micrometer, 10 nm to 500 nm, 10 nm to 90 nm, and 40 nm to 70 nm. Smaller particle sizes, especially those below approximately 100 nm, can be advantageous for achieving high optical transparency or transmission of the starting material and for facilitating printing. Controlling the particle size distribution, e.g.,Monodisperse, bimodal or trimodal size distributions can be advantageous to control the rheological properties, increase the weight fraction of the filler or influence the properties of the starting material and / or the object in a desired manner.

[0069] In one embodiment, an additive can be a substance that adapts the refractive index of the liquid or pasty components to the filler. An example of such a substance is polyethylene glycol (PEG) or derivatives thereof, in particular polyethylene glycol diacrylate (PEGDA) or derivatives thereof. Further examples of substances for adapting the refractive index include halogenated, in particular iodinated, substances. When using such a substance, fillers with an unadapted refractive index or fillers with particle sizes above 50 nm, in particular above 100 nm, further in particular above 500 nm, further in particular above 1 µm, and further in particular above 10 µm, can be used.

[0070] Other examples of additives are thixotropes and rheology modifiers. Suitable thixotropes and rheology modifiers include, for example, urea derivatives; modified urea compounds such as Rheobyk 410 and Rheobyk-D 410 (available from BYK-Chemie GmbH); pyrogenic metal oxides (also referred to as fumed metal oxides), including but not limited to pyrogenic silica and pyrogenic alumina; zirconium dioxide; precipitated metal oxides, including but not limited to precipitated silica and precipitated alumina; unmodified and organically modified layered silicate clays; dimer and trimer fatty acids; polyether phosphates; oxidized polyolefins; hybrid oxidized polyolefins with polyamide; alkali-soluble / swellable emulsions; cellulose ethers; hydrophobically modified alkali-soluble emulsions; hydrophobically modified ethylene oxide-based urethane; and sucrose benzoate. Ester-terminated polyamides; tertiary amide-terminated polyamides; polyalkylenoxy-terminated polyamides; polyetheramides;Acrylamidomethyl-substituted cellulose ester polymers; polyethyleneimine; polyurea; organotones; hydrogenated castor oil; organic base salts of a clay mineral (e.g., montmorillonite) and other silicate-like materials; aluminum, calcium, and zinc salts of fatty acids, such as lauric or stearic acid.

[0071] Thermally reversible gelling agents, such as ester-terminated polyamides, tertiary amide-terminated polyamides, polyalkylenoxy-terminated polyamides, and polyetheramides, as well as combinations thereof, are suitable for use as thixotropes. Examples include Crystasense LP1, Crystasense LP2, Crystasense LP3, Crystasense MP, Crystasense HP4, Crystasense HP5, Rheoptima X17, Rheoptima X24, Rheoptima X38, Rheoptima X58, Rheoptima X73, and Rheoptima X84 (available from Croda). Crystasense HP-5 is a preferred example of a thixotrope.

[0072] Other examples include metal oxides, especially metal oxides that have been surface-treated to impart certain dispersibility properties compatible with the starting material.

[0073] A thixotrope can be present in the starting material in an amount of, for example, about 0.05 wt.% to about 15 wt.%, particularly about 0.5 wt.% to about 15 wt.%, further particularly about 0.5 wt.% to about 10 wt.%, and further particularly about 1 wt.% to about 10 wt.%. In principle, a thixotrope is preferably present in an amount effective in restricting the movement of the three-dimensional object, or one or more regions thereof, within the starting material during the object's formation. Preferably, the thixotrope is present in the starting material in an amount effective in restricting the movement of the object, which floats (without contact with a container surface) in the working volume during formation. The orientation and / or position of the object within the working volume remains (essentially) unchanged during the formation process.

[0074] An example of a defoamer mentioned above, which can be used to assist in the elimination of bubbles that occur during processing and handling, is BYK 1798 (a silicone-based defoamer) (available from BYK-Chemie GmbH).

[0075] Furthermore, it is generally accepted that the starting material may contain water. The starting material can therefore be an aqueous solution. The water content can be between 5 and 99.9 wt.%, in particular between 30 and 99.9 wt.%, further in particular between 40 and 99.9 wt.%, further in particular between 50 and 99.9 wt.%, further in particular between 60 and 99.9 wt.%, further in particular between 70 and 99.9 wt.%, further in particular between 80 and 99.9 wt.%, further in particular between 90 and 99.9 wt.%. InSuch embodiments may contain appropriate additives, such as rheology modifiers, e.g., in the form of polyacrylic acid, gelatin, etc., which are soluble in or miscible with water or water-monomer or water-oligomer mixtures. The corresponding solubility or miscibility of the additives in or with water should be ensured, in particular, within a temperature range between 20 and 40°C, especially between 25 and 37°C, alternatively between 20 and 30°C, or further alternatively between 35 and 40°C.

[0076] The corresponding aqueous starting materials, in particular those containing one or more water-soluble and / or water-miscible additives, are selected in their composition to be transparent. This means, in particular, that the starting material, even with additives, exhibits a transmission of at least 30%, at least 50%, at least 80%, and at least 90% in the region of incident light of the first wavelength and / or in the region of incident light of the second wavelength, particularly in a wavelength range between 370 and 800 nm, especially between 400 and 800 nm. The transmission refers to an optical path length of 10 mm according to the Lambert-Beer law.Adequate transmission should be ensured, particularly in a temperature range between 20 and 40°C, especially between 25 and 37°C, alternatively between 20 and 30°C, or alternatively between 35 and 40°C.

[0077] Suitable aqueous starting materials, particularly those containing one or more water-soluble and / or water-miscible additives, are selected in their composition to have a pH value in the range of 5 to 10, particularly between 6 and 9, further specifically between 7 and 8, and further specifically between 7.4. This prevents or at least reduces undesirable precipitation of additives and / or undesirable emulsion formation. The pH value can be adjusted or stabilized by adding a buffer, such as a phosphate-buffered saline solution (PBS). A suitable pH value should be maintained, particularly within a temperature range of 20 to 40°C, specifically between 25 and 37°C, or alternatively between 20 and 30°C, or further alternatively between 35 and 40°C.

[0078] In general, it can be advantageous for the printing process if the pH value of the starting material is above 8, particularly above 8.5, and especially above 9. A corresponding pH value allows for a wider printing and processing window. Furthermore, a corresponding pH value typically has a positive effect on the rheological properties of the starting material as well as on its optical properties, especially its transparency.

[0079] As a further conceivable additive, the starting material can contain one or more of the following gelling agents, which can also serve as rheology modifiers. A gelling agent can be, for example, a polymer, in particular a polymer with carboxylic acids, such as polyacrylic acid, or cross-linked polyacrylic acid; or a polyvinyl alcohol or a derivative thereof; or a polysaccharide or a derivative thereof; or a peptide or protein or a derivative thereof, in particular gamma-carrageenan; or gelatin or a derivative thereof. The addition of a gelling agent, or more generally a rheology modifier, is preferred when the starting material contains a low-viscosity monomer or oligomer. The addition of a rheology modifier has proven particularly advantageous when the starting material is a polyethylene glycol diacrylate derivative (PEGDA), in particular with a proportion of at least 10 wt.%, in particular at least 20 wt.%, and further, in particular at least 30 wt.%.-%, further in particular at least 40 wt.%, further in particular at least 50 wt.%, further in particular at least 60 wt.%, further in particular at least 70 wt.%, further in particular at least 80 wt.%, further in particular at least 90 wt.%, contains.

[0080] InIn one embodiment, light of the first wavelength can be irradiated first into the first layer volume and then into the second layer volume with a substantially homogeneous distribution with respect to at least one of the following light parameters: light intensity and light color. In this way, substantially homogeneous illumination of the respective layer volume can be achieved. Alternatively, it can be provided that the light of the first wavelength is irradiated first into the first layer volume and then into the second layer volume with a non-homogeneous distribution with respect to at least one of the light parameters, whereby the inhomogeneous distribution in the first layer volume may differ from the inhomogeneous distribution in the second layer volume. For example, a gradient in light intensity can be formed for the light of the first wavelength across the width and / or height of the layer volume.

[0081] The light of a second wavelength can be projected first onto the first layer volume and then onto the second layer volume, each with a non-homogeneous distribution with respect to at least one of the following light parameters: light intensity and light color. While the light of the first wavelength can illuminate the respective layer volume as homogeneously or uniformly as possible, the light of the second wavelength does not illuminate the starting material in the layer volume homogeneously, but rather according to the non-homogeneous light distribution of the projected light (of the second wavelength) in order to optically process this non-homogeneous light distribution (light parameters). This enables the formation or creation of a spatial outer contour. Optionally, different non-homogeneous light distributions (different projections) can be applied to each layer volume.

[0082] When irradiating the first layer volume and / or the second layer volume with light of the first wavelength, a layer volume with a thickness of at most approximately 1 mm can be irradiated or detected. Alternatively, a layer volume with a thickness of at most approximately 500 µm can be irradiated. In a further alternative embodiment, a layer volume with a thickness of at most approximately 250 µm can be irradiated. A minimum layer thickness for irradiated layer volumes can be approximately 10 µm.

[0083] From the starting material, a plurality of optical elements can also be formed (at least partially) by means of optical processing.

[0084] The formation of the at least one optical element can comprise the formation of at least one optical lens, an imaging lens, an intraocular lens, a lens array, a diffuser, a prism, an optical grating, a diffractive optical element, and an optical waveguide. The intraocular lens can, in particular, be an accommodating intraocular lens. The formation of a (functional) contact lens can also be provided. In other words, the method can be used to produce, in particular, an optical lens, an imaging lens, an intraocular lens (especially an accommodating intraocular lens), a lens array, a diffuser, a prism, an optical grating, a diffractive optical element, or an optical waveguide.

[0085] In one embodiment, the optical element can be formed with a transmission of at least 10%, in particular at least 20%, further in particular at least 30%, further in particular at least 40%, further in particular at least 50%, further in particular at least 60%, further in particular at least 70%, further in particular at least 80%, further in particular at least 90%, in a range from 300 nm to 2500 nm, preferably from 380 nm to 2000 nm, more preferably from 400 nm to 1800 nm, most preferably from 450 nm to 1600 nm. InIn another embodiment, the optical element can be formed with a surface roughness (rms) of at most 100 nm, preferably at most 50 nm, more preferably at most 30 nm, and most preferably at most 10 nm. The transmission refers in particular to a thickness or wall thickness of the optical element or an optical path length of 1 mm or 10 mm according to the Lambert-Beer law of the optical element. The smallest individual structures of the optical element can have a size of 0.1 µm to 10 µm.

[0086] It should be noted here that an optical element within the meaning of the application is any element that exhibits a transmission of at least 10%, particularly at least 20%, further particularly at least 30%, further particularly at least 40%, further particularly at least 50%, further particularly at least 60%, further particularly at least 70%, further particularly at least 80%, further particularly at least 90%, in a wavelength range of 300 nm to 2500 nm, preferably from 380 nm to 2000 nm, more preferably from 400 nm to 1800 nm, and most preferably from 450 nm to 1600 nm. The transmission typically refers to a thickness or wall thickness of the optical element or an optical path length of 1 mm according to the Lambert-Beer law of the optical element.

[0087] The optical element can be designed to shape light. In particular, the optical element can be designed to refract, diffract, reflect, scatter, interfere, and / or polarize light. The optical element can be formed as at least one of a spherical lens, an aspherical lens, a freeform lens, a Fresnel lens, a lens array, a diffuser, a prism, an optical grating, a diffractive optical element, and an optical waveguide.

[0088] Further processing of the green body can be free of photochemical post-curing and / or tempering and / or further process steps such as grinding, polishing and / or coating, especially for the formation of the optical element with low surface roughness.

[0089] The starting material may include at least one functional element, particularly before and / or during optical processing. Furthermore, the optical element may be formed at least partially adjacent to the at least one functional element. In particular, the optical element may be formed around the at least one functional element, preferably such that the formed optical element at least partially (and especially completely) encloses the at least one functional element.

[0090] The at least one functional element can be arranged at least partially, and in particular completely, in the starting material and / or at least partially in contact with the starting material. It may be provided that the at least one functional element is arranged in the starting material by means of an arrangement device.

[0091] The at least one functional element can comprise at least one of the following: an actuator element, a sensor element, an energy source element (for providing electrical energy, for example, a solar cell), a display, a lens holder (lens mount), and a prefabricated additional optical element. Additionally or alternatively, the at least one functional element can comprise at least one optical component, in particular at least one of one or more apertures and optical filters.

[0092] The at least one additional prefabricated optical element can be a lens, a lens array, an optical grating, a diffractive optical element, or an optical waveguide. The optical element can, in particular, be bonded to an optical fiber and / or a light source.

[0093] The at least one functional element can comprise an optoelectronic component, in particular at least one consisting of a light source (for example, an LED chip or a laser diode) and an optical sensor (for example, a CMOS or CCD chip).

[0094] The at least one functional element may comprise at least one electronic component, in particular at least one of an electronic circuit, a resistive sensor, an electronic chip, a battery, an electrical line and an electrical connection.

[0095] The at least one functional element can comprise at least one component with surface connections, preferably enabling the control of another electronic functional element inside the component. The at least one functional element can comprise at least one micropump or one mechanical actuator.

[0096] The at least one functional element can have a refractive index equal to or similar to that of the starting material, in particular such that no refraction of first and / or second wavelength light occurs at the interface between the functional element and the starting material. The at least one functional element can have (and / or be formed with) a refractive index that deviates from the refractive index of the starting material by at most 3%, preferably at most 1%, particularly preferably at most 0.3%, and particularly preferably at most 0.1% (relative).

[0097] At least one functional element can be non-reflective.

[0098] The process may further include finalizing the (at least partially) formed optical element. The process may involve laser processing and / or mechanical processing of the optical element. Laser processing and / or mechanical processing of the optical element are conceivable examples of finalizing the (at least partially) formed optical element.

[0099] During optical processing, the starting material can be irradiated around the at least one functional element with light of a first wavelength and light of a second wavelength from at least two sides, in particular two different sides, and further, in particular, from four different sides. The irradiation from at least two sides, in particular two sides, and further, in particular, four sides, can be simultaneous or successive. For example, the optical processing of the functional element can be carried out in a first direction and (simultaneously or successively) in a second direction different from the first direction. In particular, the functional element can be rotated relative to the light source(s) between optical processing in the first direction and optical processing in the second direction.

[0100] Irradiation can be carried out using light sources arranged opposite each other (first wavelength and / or second wavelength), in particular such that the starting material is arranged between the oppositely arranged light sources.

[0101] Irradiation with light of the first wavelength and / or light of the second wavelength can be carried out using multiple light sources, such that the light is preferably directed into layer subvolumes that are at least partially superimposed. The at least one functional element can be arranged in the initial volume such that it does not obstruct, or obstructs as little as possible, the beam paths of the light of the first and second wavelengths. In particular, multiple light sources can be used to provide the light of the first and / or second wavelength in order to reach all subvolumes around the functional element.

[0102] Alternatively, the light from a light source can be directed into the output volume via an arrangement of light-reflecting elements, in particular mirrors, such that all subvolumes around the functional element can be irradiated. Optionally, non-adjacent subvolumes can be irradiated sequentially, wherein, in particular, a portion of the output volume is first processed in one direction and then another portion of the output volume is processed in a different direction, preferably the opposite direction. In cases where it is not possible to irradiate all subvolumes around the functional element, the described methods can be used to minimize the inaccessible subvolume.

[0103] In particular, light of the first wavelength can be directed into the starting material by means of a mirror ring, wherein the starting material is arranged inside the mirror ring and / or along an axis of rotation of the mirror ring. In this way, a circular light section can be formed for the light of the first wavelength. The light of the second wavelength can be directed into the starting material orthogonally to the light section.

[0104] In one embodiment, both a light section of the first wavelength and the projector image of the second wavelength can be generated by a (single or integrated) projection device and then projected onto / into the receiving vessel. An arrangement of light-reflecting elements, in particular mirrors, can be provided to split the light section from a beam axis of the projection device and to project the light section perpendicular to the projection image into the receiving vessel.

[0105] In one embodiment, the receiving vessel can be moved to guide the light section through the working volume. The projected image can be focused sharply within the light section using variable focus optics. In another embodiment, the direction of movement can be changed during the process so that parts of the working volume are cured in different directions. In a further embodiment, the receiving vessel remains stationary, and the light section is moved, for example, by dividing a display element of the projection device, such as an LCD or DM display, into a central area that generates the projected image and two areas located to the sides that generate the light section. For this purpose, pixels of the display element can be controlled by adjusting the optical transmission and / or reflection of the display element to achieve a lateral shift of the light section.In this process, a central area of ​​the display element can be irradiated with the first wavelength and outer areas of the display element with the second wavelength.

[0106] It may be possible to illuminate the material being processed with light of (at least) a third wavelength, where the third wavelength differs from the first and second wavelengths. The third wavelength light can be illuminated simultaneously with, or with a time delay from, the light of the second / first wavelength onto a currently processed layer volume. The projection device or a separate projection device can be used to selectively limit the light illumination to the current layer volume. This allows for the (complementary) influence of chemical / physical processes initiated or occurring within the working volume of the material being processed, for example, in the use of polychrome multiphoton polymerization.

[0107] Further exemplary embodiments of the method are explained below: InIn one embodiment, the starting material, particularly after being placed in a container defining the working volume, can be left to stand for a certain period of time, in particular for at least one hour, in particular for at least six hours, further in particular for at least twelve hours, further in particular for at least eighteen hours, further in particular for at least twenty hours. Such a period of standing of the starting material can, as mentioned above, lead to the establishment of desired rheological properties of the starting material, i.e., in particular a desired yield point.

[0108] InIn one embodiment, the starting material can be subjected to at least one process for removing impurities, particularly particulate impurities, before irradiation, especially before being filled into a container defining the working volume. This process particularly includes filtering the starting material by means of a filter device. Thus, any impurities that could negatively affect the optical properties of the optical element to be manufactured can be removed, which has a correspondingly positive effect on the quality of the optical element to be manufactured.

[0109] InIn another embodiment, further processing of the green compact, such that an optical element is at least partially, and in particular completely, formed from the green compact, can be carried out, in particular post-curing of the green compact, under a protective gas atmosphere, especially an argon, carbon dioxide, or nitrogen atmosphere. Surprisingly, it was found that further processing of the green compact, in particular post-curing of the green compact, and further, in particular, photochemical and / or thermal post-curing of the green compact, under a suitable protective gas atmosphere leads to improved component surfaces. Specifically, undesirable sticky component surfaces can be avoided or at least reduced in this way.

[0110] InIn a further embodiment, the further processing of the green compact can include photochemical post-curing of the green compact by means of at least one additional photoinitiator, wherein the additional photoinitiator is configured to carry out a photochemical reaction that causes photochemical post-curing of the green compact at a wavelength different from the first and second wavelengths. Thus, photochemical post-curing of the green compact can advantageously be carried out with an additional photoinitiator that exhibits no or minimal absorption at the first and second wavelengths, ensuring that the additional photoinitiator does not react, or hardly reacts, when the starting material is irradiated with light of the first and second wavelengths.

[0111] An example of a suitable additional photoinitiator is an alpha-diketone, in particular camphorquinone; or, a suitable additional photoinitiator can contain at least one alpha-diketone, in particular camphorquinone. Such additional photoinitiators have proven particularly useful when the first wavelength is below 400 nm, especially at 375 nm, and the second wavelength is at or above 500 nm.

[0112] In general, an additional photoinitiator can be used that has an absorption maximum between the first and second wavelengths. An example of such an additional photoinitiator is an alpha-diketone, in particular camphorquinone, whose absorption maximum is at approximately 470 nm. In an embodiment of the method where the first wavelength is below 420 nm and the second wavelength is above 500 nm, the absorption maximum of camphorquinone therefore lies between these two wavelengths.

[0113] Generally, an additional photoinitiator can be used that exhibits absorption in the wavelength range between 400 and 600 nm. As mentioned, the absorption maximum of the additional photoinitiator can lie between the first and second wavelengths.

[0114] In general, an additional photoinitiator can be used which, when irradiated with light of a wavelength between the first and second wavelengths, changes its optical properties, i.e., in particular, bleaches.

[0115] In general, an additional photoinitiator can be used which has an extinction coefficient of less than 10000 L / mol / cm, in particular less than 5000 L / mol / cm, further in particular less than 1000 L / mol / cm, further in particular less than 500 L / mol / cm, further in particular less than 300 L / mol / cm, further in particular less than 100 L / mol / cm, further in particular less than 50 L / mol / cm, further in particular less than 10 L / mol / cm, further in particular less than 1 L / mol / cm.

[0116] An additional photoinitiator can be: an alpha-diketone, such as diacetyl, 3,4-hexanedione.

[0117] Alternatively or additionally, an additional photoinitiator can be: an aromatic alpha-diketone, such as benzil or a benzil derivative, or acenaphthenquinone.

[0118] Alternatively or additionally, an additional photoinitiator can be: a cyclic alpha-diketone, such as camphorquinone or 1,2-cyclohexanedione.

[0119] Alternatively or additionally, an additional photoinitiator can be: an aliphatic alpha-diketone, such as camphorquinone, diacetyl or 3,4-hexanedione.

[0120] In general, an additional photoinitiator may be present, for example, in a specific concentration of 0.0001 to 10 wt.%, in particular between 0.01 and 2 wt.%, further in particular between 0.1 and 2 wt.%, further in particular between 0.1 and 1 wt.%.

[0121] The use of an additional photoinitiator is advantageous, which can be irradiated with visible light, particularly light in a wavelength range between 400 and 600 nm, preferably between 420 and 500 nm. Since the additional photoinitiator, as mentioned, can be excited particularly between the first and second wavelengths and exhibits hardly any absorption at these wavelengths, it does not, or hardly, impair the absorption of the starting material at these wavelengths. This results in a high penetration depth for the first and second wavelengths during the formation of the object or green body, thus maximizing the build volume and preventing or at least reducing undesirable side reactions at the first and second wavelengths. Furthermore, homogeneous post-curing of the object can be achieved even within the working volume. For example, this allows for...Cracks in the surface of the object are prevented or at least reduced; this is not the case if the additional photoinitiator is irradiated with light of a wavelength below the first wavelength.

[0122] In one embodiment, the post-processing, in particular post-curing, of the object, especially when using a suitable additional photoinitiator, can include irradiating the object with light of a wavelength between the first and second wavelengths. As mentioned, this can, for example, prevent or at least reduce cracks in the surface of the object; this is not the case if the additional photoinitiator is irradiated with light of a wavelength below the first wavelength. This may, if applicable, constitute a separate aspect of the invention.

[0123] In one embodiment, the green compact can be irradiated with light of a wavelength lying between the first and second wavelengths, whereby the absorption decreases at at least one wavelength lying between the first and second wavelengths. In this way, the penetration depth for the light used for post-processing can be increased during irradiation, thereby enabling efficient post-processing, particularly of the inner part of the green compact, resulting in a homogeneously hardened optical element. This may optionally constitute a separate aspect of the invention.

[0124] In one embodiment, the green compact can be irradiated with light of a wavelength lying between the first and second wavelengths, whereby absorption decreases in the wavelength range between the first and second wavelengths. In this way, the penetration depth for the light used for post-processing can be increased during irradiation, thereby enabling efficient post-processing, particularly of the inner part of the green compact, resulting in a homogeneously hardened optical element. This may optionally constitute a separate aspect of the invention.

[0125] In one embodiment, the green compact can be irradiated with light of a wavelength lying between the first and second wavelengths, whereby absorption decreases at the irradiation wavelength lying between the first and second wavelengths. In this way, the penetration depth for the light used for post-processing can be increased during irradiation, thereby enabling efficient post-processing, particularly of the inner part of the green compact, resulting in a homogeneously hardened optical element. This may optionally constitute a separate aspect of the invention.

[0126] In a further embodiment, the further processing of the green compact can include treating the green compact with a solvent and / or a monomer, in particular for washing the green compact, wherein a solvent and / or a monomer with a molar mass greater than or equal to 200 g / mol is used. By using a solvent or monomer with a correspondingly high molar mass, it can be prevented that the solvent or monomer penetrates the green compact, which could impair its properties.

[0127] A specific example of a suitable solvent or monomer is tripropylene glycol monomethyl ether with a corresponding molar mass.

[0128] In a further embodiment, the further processing of the green compact can include treating it with a solvent and / or a monomer, particularly for washing, using a highly volatile solvent and / or a highly volatile monomer. The use of a highly volatile solvent or monomer can accelerate the drying process of the green compact and thus make the process even more efficient.

[0129] A concrete example of a suitable solvent or monomer of low molecular weight is an alcohol, such as ethanol or isopropanol.

[0130] In a further embodiment, a starting material free of inorganic and / or organic particles can be used. In particular, a starting material free of inorganic and / or organic particles with a diameter greater than 50 µm can be used. This can also have a positive effect on the quality of the optical element produced according to the process, especially because no impairment by inorganic and / or organic particles or nanoparticles is possible. The starting material can nevertheless contain inorganic and / or organic nanoparticles, i.e., in particular particles with a diameter of less than 50 nm, for example, to adjust a desired refractive index. Such nanoparticles can be present, for example, in a concentration between 0.1 and 5 wt.%, in particular between 0.3 and 2 wt.%, and further, in particular between 0.5 and 1.5 wt.%.Suitable nanoparticles can be, for example, SiO2, ZrO2 and TiO2 nanoparticles.

[0131] In another embodiment, a starting material can be used that contains exclusively organic components. This can also have a positive effect on the quality of the optical element produced according to the process, particularly because no impairments by inorganic components are possible.

[0132] In another embodiment, a starting material free of organic polymers can be used. This can also have a positive effect on the quality of the optical element produced according to the process, particularly because there is no possibility of impairment by organic polymers, which could potentially lead to undesirable polymerization-related phase separations.

[0133] In a further embodiment, the optical element to be manufactured can have a planar geometric shape with a principal plane of extension. This applies, for example, to optical lenses. In such embodiments, the build-up or printing direction of the optical element is expediently chosen to be perpendicular, in particular perpendicular, to the principal plane of extension. In this way, any settling of the green compact in the starting material, which could potentially have a negative impact on the quality of the optical element to be manufactured, can be prevented or at least slowed down.

[0134] In principle, it is conceivable for all embodiments that the build-up or printing direction is chosen from top to bottom, or vice versa. The build-up or printing direction can therefore be aligned along a vertical axis.

[0135] In another embodiment, the first wavelength can be less than or equal to 400 nm, in particular less than or equal to 375 nm. Alternatively or additionally, the second wavelength can be 405 nm.

[0136] InIn a further embodiment, the starting material and / or the photoinitiator and / or a co-initiator can be free of amine compounds or contain less than 10 wt.%, in particular less than 5 wt.%, further in particular less than 4 wt.%, further in particular less than 3 wt.%, further in particular less than 2 wt.%, further in particular less than 1 wt.%, further in particular less than 0.5 wt.%, further in particular less than 0.25 wt.%, further in particular less than 0.1 wt.%, of one or more amine compounds. This can also have a positive effect on the quality of the optical element to be produced according to the process, in particular because undesirable interactions of corresponding amine compounds with the starting material can be avoided, which may have a negative impact on the component quality of the optical element to be produced. In particular, undesirable coloring orTo prevent or at least reduce discoloration, especially undesirable yellowing, of the optical element to be manufactured.

[0137] InIn a further embodiment, at least one first irradiation device can be used, configured to emit light of the first wavelength into the working volume to generate at least one first light projection in the working volume, wherein the at least one first light projection comprises several light beams that traverse the working volume in at least one plane of light. Furthermore, at least one light modulation device can be used, associated with the at least one first irradiation device, wherein the at least one light modulation device is configured to modulate the spatial direction of extension of two or more of the several beams in the at least one plane of light such that the two or more light beams extend in a non-parallel arrangement relative to each other.

[0138] The at least one light modulation device is configured to modulate the spatial direction of extension of two or more light beams from the multiple beams of the at least one light plane such that the two or more light beams are arranged in a non-parallel configuration relative to each other. The at least one light modulation device can be configured to actively and / or passively change the spatial direction of extension and / or orientation of two or more light beams from the multiple beams in the at least one light plane such that at least two of the multiple light beams are arranged in a non-parallel configuration relative to each other. The non-parallel arrangement of the at least two light beams in the at least one light plane typically results in the at least two light beams intersecting at at least one intersection point within the at least one light plane. In particular, multiple intersection points,where at least two light beams intersect, at different positions within the at least one light plane. In contrast to the light planes of conventional volumetric 3D printing devices, which comprise an (essentially) parallel arrangement of (collimated) light beams without intersecting light beams, the at least one light modulation device of the device described here enables a targeted change in the spatial direction of extension and / or orientation of at least two light beams within the at least one light plane, such that the at least two light beams are arranged in a non-parallel configuration.so that the at least two light rays are arranged in a non-parallel arrangement relative to each other within the at least one plane of light, resulting in one or more points of intersection being created within the at least one plane of light, where two or more light rays cross.

[0139] In particular, the at least one light modulation device can be configured to influence the optical coherence of light rays within the at least one light plane, in particular to reduce it at least partially, by selectively changing the spatial direction of extension and / or orientation of at least two light rays so that at least two light rays run in a non-parallel arrangement to each other, resulting in two or more light rays crossing at one or more points of intersection within the at least one light plane.A change in the spatial direction and / or orientation of at least two light rays, such that at least two light rays are not parallel to each other in the at least one plane of light, also results in the at least one plane of light containing light rays with angled spatial directions of extension as they traverse, pass through, or propagate through the working volume. In particular, at least two light rays can traverse, pass through, or propagate through the working volume at an angle to each other other than 0°. An intersection of at least two light rays at one or more points of intersection within the at least one plane of light can also consist of at least two light rays being able to superimpose at the one or more points of intersection.

[0140] The at least one light modulation device can thus be configured to direct two or more light beams within the at least one plane of light, e.g., by diffraction and / or refraction and / or scattering, such that the at least one plane of light comprises non-parallel and / or non-coherent light beams. Directing light beams can include changing the spatial direction of propagation of one or more light beams, particularly with respect to an original spatial direction of propagation, such that the at least one plane of light comprises non-parallel and / or non-coherent light beams. This is precisely the opposite operating principle of conventional light sheet generators, which are designed to generate light sheets from non-overlapping collimated light beams, i.e., light beams with parallel spatial directions of propagation without overlap. This results in the following: unlike conventional light sheets, the light sheet generators...Light sections that essentially have a rectangular basic shape, defined vertically by a parallel arrangement of uppermost and lowermost light rays, where at least one light section, which is modified by the at least one light modulation device, may have a non-rectangular basic shape, such as a trapezoidal shape, defined vertically by non-parallel light rays, within the working volume.

[0141] In particular, the at least one light modulation device can be configured to generate modified light beams with properties other than a Gaussian beam. For example, the at least one light modulation device can be configured to generate modified light beams that have a non-Gaussian beam profile. For instance, the at least one light modulation device can be configured to generate modified light beams, such as Airy beams or Bessel beams, or light beams with characteristics similar to, for example, Airy beams or Bessel beams.

[0142] Surprisingly, experiments have shown that by selectively generating specific intersection points where two or more light beams cross in at least one light plane, undesirable artifacts and thus undesirable properties, such as (quasi-)regular or irregular fringe or striae artifacts, can be significantly reduced. This results in an optical appearance of the manufactured green body as if it were built up layer by layer, as is the case, for example, with conventional additive manufacturing using stereolithography principles and / or digital light processing principles and / or volumetric printing processes such as computed axial lithography (CAL). The at least one light modulation device thus has a positive effect on the properties of the three-dimensional objects produced with the device.

[0143] The at least one light modulation device may comprise one or more optical elements, each optical element being configured to change the original spatial direction of an incident light beam in order to produce a light beam having a different spatial direction of extension relative to the original spatial direction of extension. The optical elements may, for example, be configured as or include optical lenses, in particular microlenses, and / or optical diffuser elements, in particular elliptical diffuser elements.

[0144] The light modulation device can be movably mounted in at least one translational and / or rotational degree of freedom, particularly relative to the working volume. In particular, the light modulation device can be movably mounted in a uniform or oscillating motion in at least one spatial direction. For this purpose, a corresponding drive coupled to the light modulation device, in particular including associated control equipment, can be provided.

[0145] In principle, reflective and / or diffractive optical elements are suitable. It is conceivable that at least one optical element of the at least one light modulation device comprises, for example, a combination of at least two of: one or more optically transparent surfaces, one or more optically reflective surfaces, and / or one or more optically diffracting surfaces; or a combination of at least two optically transparent surfaces, optically reflective surfaces, and / or optically diffracting surfaces. Such optically transparent surfaces and / or optically reflective surfaces and / or optically diffracting surfaces can, for example, be formed by or comprise one or more optically transparent coatings and / or reflective coatings and / or optically diffracting coatings.

[0146] In a further embodiment, at least one measure can be taken to modify the optical properties of the green compact. This ensures that the green compact has the desired optical properties, i.e., in particular, the desired transmission.

[0147] The at least one measure may preferably include a change in the optical properties of the green body, leading to a reduction in the absorption properties of the green body or the optical element for at least one wavelength in a wavelength range between 300 nm and 2000 nm, in particular between 350 nm and 900 nm, and / or to an increase in the light transmission properties of the green body or the optical element for at least one wavelength in the wavelength range between 300 nm and 2000 nm, in particular in the wavelength range between 350 nm and 900 nm, and in particular in the wavelength range between 400 nm and 800 nm.

[0148] The at least one measure for carrying out at least one measure to modify the optical properties of the green body may include the modification of the optical properties of the green body, resulting in a mean transmission or integral of the transmission between 300 nm and 2000 nm, in particular between 350 nm and 900 nm, in particular between 400 nm and 800 nm, by at least 1%, in particular at least 2%, in particular at least 3%, in particular at least 4%, in particular at least 5%, in particular at least 7.5%, in particular at least 10%, in particular at least 15%, in particular at least 20%, in particular at least 25%, in particular at least 30%, in particular at least 35%, in particular at least 40%, in particular at least 45%, in particular at least 50%, in particular compared to a state of the green body before it was subjected to the at least one measure.Alternatively or additionally, the at least one measure for modifying the optical properties of the green body may include modifying the optical properties of the green body in such a way that the mean absorption or integral of the absorption between 300 nm and 2000 nm, in particular between 350 nm and 900 nm, in particular between 400 nm and 800 nm, is reduced by at least 1%, in particular at least 2%, in particular at least 3%, in particular at least 4%, in particular at least 5%, in particular at least 7.5%, in particular at least 10%, in particular at least 15%, in particular at least 20%, in particular at least 25%, in particular at least 30%, in particular at least 35%, in particular at least 40%, in particular at least 45%, in particular at least 50%, in particular compared to a state of the green body before it was subjected to the at least one measure.

[0149] An optical element can therefore generally be understood to be any element which has an average or integrated absorption per mm thickness of the element for each wavelength in the wavelength range between 300 nm and 2000 nm, in particular between 400 nm and 900 nm, further in particular between 500 nm and 850 nm, further in particular between 600 nm and 800 nm, further in particular between 650 nm and 750 nm, of less than 0.5, in particular less than 0.3, in particular less than 0.2, in particular less than 0.1.

[0150] The at least one measure may include modifying the optical properties of the green body, resulting in an average or integrated absorption per mm thickness of less than 0.5, in particular less than 0.3, more specifically less than 0.2, and more specifically less than 0.1, in a wavelength range between 300 nm and 2000 nm, in particular between 350 nm and 900 nm, and more specifically between 400 nm and 800 nm. In particular, the average or integrated absorption per mm thickness of the green body for each wavelength in the wavelength range between 300 nm and 2000 nm, in particular between 350 nm and 900 nm, and in particular between 400 nm and 800 nm, may be less than 0.5, in particular less than 0.3, in particular less than 0.2, and in particular less than 0.1.

[0151] In particular, the average or integrated absorption per mm thickness of the optical element for each wavelength in the wavelength range between 300 nm and 2000 nm, in particular between 350 nm and 900 nm, in particular between 400 nm and 800 nm, can be less than 0.5, in particular less than 0.3, in particular less than 0.2, in particular less than 0.1.

[0152] The at least one measure may include, for example, thermal treatment of the green body and / or optical treatment of the green body, in particular by irradiating the green body with electromagnetic radiation, and / or chemical treatment of the green body.

[0153] The thermal treatment may involve exposing the green body to temperatures between 50 and 150°C, particularly between 75 and 125°C, especially for a duration between 1 and 24 minutes, further particularly between 1 and 20 minutes, further particularly between 1 and 16 minutes, further particularly between 1 and 12 minutes, further particularly between 1 and 8 minutes, further particularly between 1 and 4 minutes, further particularly between 1 and 30 minutes.

[0154] The optical treatment may involve irradiating the green body with electromagnetic radiation of a wavelength between 350 nm and 1000 nm, in particular between 400 nm and 800 nm, and further in particular between 350 nm and 500 nm or between 420 nm and 800 nm, in particular for a duration between 0.5 and 180 min, between 5 and 60 min.

[0155] The optical treatment of the green body can be carried out in the working volume or after the green body has been removed from the working volume.

[0156] The three-dimensional object can subsequently be subjected to optical treatment of tempering, wherein the tempering may in particular include heating the green body to a temperature in the range between 50°C and 150°C for a time in the range between 1 min and 60 min, in particular 5 min and 30 min.

[0157] The chemical treatment can include, for example, the chemical modification, in particular by oxidation and / or reduction of the chromophore molecules, especially the remaining photoinitiator molecules, of the green body, wherein the molecules have a (visible) color in the visible wavelength spectrum between 380 nm and 750 nanometers, with at least one chemical modifying agent, e.g. an oxidizing or reducing agent.

[0158] Specifically, the at least one chemical modifying agent may be or comprise a chlorine-based substance, in particular chlorine, hypochlorite, chlorine dioxide, or an oxygen-based substance, in particular ozone, oxygen, peroxide, perborate, percarbonate, peracetic acid, or chlorine or a chlorine compound.

[0159] The at least one chemical modifier can be added to the photopolymerized material after the formation of the green body by immersing the three-dimensional object for a certain time in a solution, in particular an organic solution, containing the at least one chemical modifier, wherein the at least one chemical modifier migrates from the solution into the three-dimensional object and optionally residual co-initiator and / or photoinitiator migrates from the three-dimensional object into the solution.

[0160] The at least one chemical modifier can be configured to change the chromophore properties of the original chromophore molecules, in particular the remaining photoinitiator molecules, of the photopolymerizable material (starting material) and / or the chromophores of the green body resulting from the photopolymerization process, or the at least one chemical modifier can be configured to generate a reactive agent configured to change the chromophore properties of the chromophore molecules, in particular the remaining photoinitiator molecules, of the green body under the influence of electromagnetic energy, in particular thermal energy and / or radiation energy.

[0161] In all embodiments, the optical processing of the starting material can also be carried out by at least one combined light section. A corresponding combined light section can be generated, for example, as follows: a first light section is generated, which extends along an axis of extension through the starting material, and a second light section is generated in which the first light section emerging from the starting material is reflected by at least one reflective element, and the reflected light section thus generated extends (essentially) along the axis of extension of the first light section again through the starting material. In principle, any light section described herein can be a corresponding combined light section.It is also conceivable that several combined light sections are used, which extend through the working volume from at least two, in particular at least three, and further, in particular at least four, different sides. The axes of extension of the respective combined light sections can be aligned at any angle to each other, i.e., at an angle of approximately 90°.

[0162] A suitable reflective element can be, for example, or comprise: at least one planar mirror, at least one single or multiply curved mirror, such as a doubly concave mirror, at least one plano-convex cylindrical lens, at least one plano-concave cylindrical lens, etc. Combinations of at least two identical or different reflective elements of the aforementioned type are conceivable. Description of exemplary implementations

[0163] In theFurther examples of implementation are explained in more detail below with reference to figures in a drawing. These show: Fig. 1 a schematic representation of a device for processing an optically reactive material from above; Fig. 2 a schematic representation of the device Fig. 1 from the side; Figs. 3a to 3c a schematic representation of an arrangement for the optical processing of a starting material in a receiving vessel; Fig. 4 a schematic representation of a further arrangement for the optical processing of a starting material in a receiving vessel; Fig. 5 a schematic representation of another arrangement for the optical processing of a starting material in a receiving vessel by means of a projection device; Fig. 6 a schematic representation of a further arrangement for the optical processing of a starting material in a receiving vessel; Fig. 7a schematic partial representation of the arrangement Fig. 6 ; Fig. 8a a schematic representation of another arrangement for the optical processing of a starting material using a mirror ring in a top view and Fig. 8b a schematic representation of the further arrangement in a side view.

[0164] Fig. 1 and 2 Figure 1 shows a schematic representation of an arrangement for a device for optically processing an optically reactive material from above and from the side. InA receiving vessel 1 contains a working volume 2, which is at least partially filled with a starting material 3. The starting material 3 can comprise one or more substances, which may be solid, liquid, or pasty. For processing, the starting material 3 is irradiated with light of a first wavelength and light of a second wavelength, which are irradiated overlappingly into the working volume 2 to trigger an optically activated reaction in a layer subvolume 4.

[0165] The light of the first wavelength is provided by means of a first light source 5, which in the illustrated embodiment is exemplified as a light section generator. During the processing of the starting material 3, a beam area 6 for the light of the first wavelength (light section), which in the illustrated embodiment is tapered, is moved step by step over the working volume 2, so that layer-by-layer processing of the starting material 3 takes place. Thus, layer subvolumes of the working volume 2, which was previously filled with the starting material 3 (layer-shaped subvolumes of the working volume 2), are irradiated successively, in particular non-overlapping layer subvolumes.

[0166] Depending on the current position of the beam area 6 (light section), the light of the second wavelength is projected by a projector 7 into the layer volume currently illuminated by the light of the first wavelength (projector or projection image). This means that the projection plane or projection volume of the projector 7 lies within the layer volume that is currently illuminated by the light of the first wavelength. The light of the first wavelength (light section) and the light of the second wavelength (light projection) thus overlap spatially or in a projection plane of the projector 7 in a macroscopic layer volume of the starting material 3, which, as a subvolume of the working volume 2, is currently illuminated by the light section.

[0167] In this way, at least one material property of the starting material 3 is altered in the currently irradiated layered subvolume, for example, by causing the original starting material to harden. Polymerization in the starting material 3 can be triggered by the interaction of light of the two wavelengths. This makes it possible, for example, to produce a three-dimensionally shaped body layer by layer in the working volume 2. The three-dimensional shaping of the body is influenced and determined by the projection of the projector 7 onto the respective layer volume.

[0168] The method allows adaptation to different volumes of the starting material 3. Furthermore, it allows optimization between resolution and processing speed.

[0169] A non-limiting example of the fabrication of an optical element is given below: Urethane dimethacrylate (genomer 4247, 350 g), ditrimethylolpropanetetraacrylate (Miramer M410, 49 g), hexanediol diacrylate (Miramer M200, 4 g), N-methyldiethanolamine (4 g), and dual-color photoinitiator 1 (50 mg) are homogeneously mixed. The optical transmission of the resulting resin was determined using a Cary 50 UVVis spectrophotometer (Varian Inc.) with an optical path length of 10 mm to be 69% at λ1 = 375 nm and >99% at λ2 = 450–800 nm. The resulting resin is transferred to a cuvette, which is optically processed according to the described procedures. The cured object is removed from the excess starting material and washed several times with isopropanol or other alcohols. The object can be post-cured by placing it in a solution of isopropylthioxanthone (ITX) in ethanol.The object is removed from the solution, air-dried, and cured by UV irradiation (365 nm). The optical element, with a thickness of 1 mm, exhibits an optical transmission >90% at 450–1600 nm and a surface roughness <0.04 µm (Ra measured according to ISO 4288:199).

[0170] The dual-color photoinitiator 1 has the following structure:

[0171] Another non-limiting example of the preparation of an optical element is given below: Urethane dimethacrylate (genomer 4247, 120 g), tricyclo[5.2.1.02,6]decandimethanol diacrylate (sartomer SR833S, 22.5 g), N-methyldiethanolamine (7.5 g), RHEOBYK-7420CA (BYK-Chemie GmbH, 5.2 g), 2,6-di-tert-butyl-4-methylphenol (BHT, 0.15 g), camphorquinone (0.15 g) and dual-color photoinitiator 2 (60 mg) are mixed homogeneously. The optical transmission of the resulting resin was determined using a Cary 50 UVVis spectrophotometer (Varian Inc.) with an optical path length of 10 mm to be 69% at λ1 = 375 nm and >99% at λ2 = 450–800 nm. The resulting resin exhibits non-Newtonian flow properties. The yield strength of the resulting resin was determined after a 24-hour settling period using rotational rheometer (Netzsch Kinexus Prime lab+ rotational rheometer, 20 mm plate-to-plate geometry, shear stress ramp: dσ / dt = 0.05 Pa / min, 25°C) to be σ = 0.8 Pa.The resulting resin is transferred to a cuvette-shaped container, which is then optically processed according to the described procedures. The cured object is removed from the excess starting material and washed several times with tripropylene glycol monomethyl ether and subsequently with isopropanol. After each wash, the object is removed from the respective washing solution, air-dried, and post-processed by irradiation with blue light (450 nm), particularly to harden it. At a thickness of 1 mm, the optical element exhibits an optical transmission >90% at 400–1600 nm and a surface roughness <0.04 µm (Ra measured according to ISO 4288:199).

[0172] The Dual-Color Photoinitiator 2 has the following structure:

[0173] When using ideal dual-color photoinitiators in the starting material 3, excitation of the active state C occurs only upon absorption of both wavelengths λ₁ and λ₂ (first and second wavelengths). For non-ideal photoinitiators, a transition from the intermediate state B to the active state C can also occur through absorption of wavelength λ₁. consequencePhotoinitiators are converted to the C state not only at the intersection of the two wavelengths, but also along the entire light beam of wavelength λ₁. Since there is no return path from the photoinitiator's active state C to the ground state A, a significant amount of initiators in the active state C accumulates in undesired regions when processing multiple desired target points. The device allows for the generation of a sufficient initiator concentration in the active state C for polymerization of the starting material in the overlapping region of the light beams, while simultaneously minimizing the generated concentration of initiator molecules in the active state C along the light beam of the first wavelength λ₁. Furthermore, the device enables the minimization of photoinitiators in the active state C in undesired regions of the volume caused by light superposition for many successive target points.

[0174] If the ground state A exhibits an absorption band at the second wavelength λ₂, the photoinitiator can be converted to the intermediate state B and subsequently to the active state C by light of wavelength λ₂. Consequently, photoinitiators are converted to state C not only at the overlap region of both wavelengths but also along the entire light beam of wavelength λ₂. Since there is no return path from the photoinitiator's active state C to the ground state A, a significant amount of initiators in the active state C accumulates in undesired regions when processing multiple desired target points. The device makes it possible to generate a sufficient initiator concentration in the active state C for the desired modification of the starting material 3 in the overlap region of the light beams, while simultaneously minimizing the generated concentration of initiator molecules in the active state C along the light beam of wavelength λ₂.Furthermore, the device should make it possible to minimize the accumulation of photoinitiators in the active state C in unwanted areas of the volume caused by the superposition of light for many successive target points.

[0175] The device and method can be combined with other techniques that limit unwanted curing through the accumulation of photoinitiators in the active state C. For example, the oxygen concentration in the starting material can be adjusted to vary the threshold at which curing occurs. Alternatively, an inhibitor can be added to the starting material to vary the curing threshold.

[0176] Further aspects of the device for optically processing the starting material 3 are explained below.

[0177] The starting material 3 can be contained in a transparent vessel (receiving vessel 1) with at least two optically planar entry windows, which receives the starting material 3 along with the added dual-color photoinitiator molecules or other optically active molecules and, optionally, further additives such as co-initiators. The light source 5, designed as a light generator with imaging optics, produces a light section of wavelength λ1, which is directed through a window of the receiving vessel 1 into the working volume 2. The projector 7, with a light source of wavelength λ2, produces an image that is sharply focused by a lens within the light section in the receiving vessel 1.

[0178] Due to the refraction of the incident light of the second wavelength at the interfaces between air and the receiving vessel 1 and between the receiving vessel 1 and the source material 3, a shift in the focal plane of the projected image (light of the second wavelength) can occur compared to the optical image without the receiving vessel 1. With large working volumes of the receiving vessel 1, the depth of field of the focused projector image may be insufficient. In this context, a focus correction can be continuously performed during the movement of the light section through the working volume 2.

[0179] For 3D printing applications, the refractive index of the starting material 3 can be similar to that of the receiving vessel 1. In this case, only the transition between air with refractive index n1 and receiving vessel 1 with refractive index n2 leads to a shift of the focal plane by the amount Δs given by: Δ s = d ⋅ n 2 n 1 − 1

[0180] As the distance d of the position of the light section (light of the first wavelength) from an entrance window of the receiving vessel 1, where the projector image enters, increases, the focus shift increases according to the equation above. This equation applies to a paraxial optical beam path and thus to larger distances between projector 7 and receiving vessel 1. Depending on the design, the shift can be compensated for by a motorized focus adjustment of the fixed projector 7 or by a motorized positioning of the entire projector 7 relative to the light section position. In the latter example, a uniform, linear relative movement of projector 7 to the fixed light section occurs during the uniform movement of the receiving vessel 1 through the light section (layer volume) for processing the entire working volume 2.

[0181] Alternatively to the one in Fig. 1As illustrated, the projector image can also enter the working volume 2 through the bottom or the lid of the receiving vessel 1, and the light section can be coupled in perpendicularly to this through one or more of the side windows.

[0182] Alternatively, the light section generator 5 can generate the wavelength λ 2, and the projector 7 generates the wavelength λ 1 .

[0183] If the transition from intermediate state B to initial state A is to be made with light of wavelength λ 3, the projector 7 generates the wavelengths λ 1 and λ 3 or the wavelengths λ 2 and λ 3 , each complementary to the wavelength of the light section generator.

[0184] One or more light detectors 8a, 8b (camera or simple photodetector; see below). Fig. 1 and 2These can be used to investigate the processes during processing by measuring the transmitted light from the excitation of the light section and, if applicable, the projector 7. The light section generator 5 and, if applicable, the projector 7 can emit further wavelengths of light that differ from the excitation wavelengths and serve only to observe the change in the material properties of the starting material 3, for example, polymerization.

[0185] Furthermore, the emitted fluorescence of excited photoinitiators located in the starting material 3 can be measured. For example, the intensity of the total transmitted or emitted light can be measured via a single photodetector and / or the spatially resolved intensity can be recorded via a camera. The detectors can selectively measure only specific wavelengths of light from the projector 7, the light section generator 5, or the light-emitting, excited photoinitiators by means of filters or spectrographs.

[0186] The evaluation of the total or spatially resolved intensities can control a control loop that influences the intensity of the light section generator, the intensity and image output of the projector, the timing of the exposure sequence, and the displacement of the light section within the receiving vessel 1. A control unit 9 is provided for this purpose, which according to Fig. 1coupled to the light source 5 and the projector 7.

[0187] A laser light source can be used as light source 5, for example, a pulsed single-mode diode laser (manufacturer: IBEAM SMART, Toptica Photonics AG, DE) with a wavelength of 375 nm and a maximum continuous-wave output power of 70 mW. The laser beam diameter is 1.3 mm (@ 1 / e 2< ). An aspherical POWELL lens (spreading angle 30°, N-BK7, Edmund Optics GmbH, DE) is used to reshape the laser beam into a diverging laser line. A plano-convex cylindrical lens with a long focal length (f = 300.00 mm, N-BK7, Thorlabs GmbH, DE) positioned directly behind it and oriented perpendicular to the spreading plane generates, in one embodiment, a beam waist with a diameter of approximately d = 100 µm at the position of the container holding the starting material, 30 cm from this lens. A plano-convex cylindrical lens (f = 150.A cylindrical lens (f = 00 mm, N-BK7, Thorlabs GmbH, DE) collimates the diverging laser line at a distance equal to the focal length of the POWELL lens, ensuring an approximately parallel beam path along the optical axis. The height of the light section after collimation is approximately 8.5 cm. A second cylindrical lens with a focal length of f = 100.00 mm (N-BK7) is flexibly positioned in front of the vessel. This lens focuses the beam path into a tapered light section, reducing the intensity drop-off within the vessel due to the Lambert-Beer absorption law. The usable height of the light section within the vessel, achieved through focusing, is approximately 2 cm.

[0188] To transform a laser beam into a diverging laser line, a suitably arranged rotating polygon mirror or a galvo scanner can be used as an alternative to the Powell lens. In principle, it is also possible to use a light source based on an LED (light-emitting diode) or a thermal light source instead of a laser.

[0189] A DMD (Digital Micromirror Device from Texas Instruments) based projector (manufacturer: optoma UHD35) with a resolution of 3840 x 2160 pixels and 3600 ANSI lumens can be used as the image projector or projector 7. The projection optics have been replaced by a projection lens with a 90mm focal length (Braun Ultralit 2.4 / 90, Braun Photo Technik GmbH, Germany), which generates a sharp image inside the container. A front-mounted filter glass (GG475, Schott AG, Germany) serves for wavelength selection. Projector 7 is controlled via an HDMI interface.

[0190] For example, a large cuvette made of optical glass (internal dimensions: 30mm x 30mm x 30mm, Hellma GmbH & Co. KG, DE) with transparent, flat entrance windows can be used as the receiving vessel 1.

[0191] In the Figs. 3a to 3cSchematic representations show an arrangement with a receiving vessel 1 in which the working volume 2, containing the starting material 3 for optical processing, is arranged. An arrangement of light sources 30 is provided. The light sources 30 (light generators for generating the light section 31), which serve to illuminate the light of the first wavelength (light section), are arranged adjacent to the receiving vessel 1, in particular on opposite sides. In the embodiment according to Fig. 3c The arrangement of light sources 30 is rotatably arranged around the receiving vessel 1 with the working volume 2, as shown schematically by means of arrows 32.

[0192] Two or more of the light sources 30 can be used, shining into the working volume 2 from different, in particular opposite or not opposite, sides of the receiving vessel 1 and generating the light section 31 by means of superposition of partial beams, i.e. illuminating the respective layer partial volume into which the projection 33 then takes place.

[0193] The light section 31 for the currently irradiated layer volume is obtained by summing the individual illuminations from the light sources 30 at different angles of incidence. In order to achieve a homogeneous intensity distribution of the light section 31 by superimposing the light from two or more light sources, the individual illuminations can exhibit a Gaussian or a modified inhomogeneous intensity distribution instead of a homogeneous one.

[0194] In further development according to Fig. 4Two or more light sections 40 (layer volumes) are generated, which fall at an angle into the receiving vessel 1. One or more projections 41 from projectors (not shown for simplicity) Fig. 4 ) produce sharp images within the individual light sections in an oblique focal plane 40. This allows the processing of several layer volumes simultaneously.

[0195] In the designs according to the Figs. 3a to 3c , 4 The receiving vessel 1 can be moved through the light section 31, 40, or the light section 31, 40 can be moved while the receiving vessel 1 is in a fixed position, in order to continuously and finally completely process the working volume 2 by optically processing its layer subvolumes one after the other.

[0196] Fig. 5Figure 1 shows schematic representations for a further arrangement with receiving vessel 1. Both a light section 50 of the first wavelength and a projector image 51 of the second wavelength are generated by means of a projection device 52 and then projected onto the receiving vessel 1. An arrangement of light reflection elements 53, in particular mirrors, ensures that the light section 50 is split off from a beam axis of the projection device 52 and that the light section 50 is projected perpendicular to the projection image 51 into the receiving vessel 1.

[0197] In one embodiment, the receiving vessel 1 can be moved to guide the light beam through the working volume 2. The projected image 51 is sharply focused within the light section 50 by means of a variable focus optic. In another embodiment, the receiving vessel 1 remains stationary, and the light section 50 is moved by dividing a display element of the projection device 52, for example an LCD or DMD display, into a central area 54, which generates the projected image 51, and two areas 55 located to the side, which generate the light section 50. For this purpose, pixels of the display element are controlled by adjusting the optical transmission or reflection of the display element to achieve a lateral displacement of the light section 50. In this process, a central area of ​​the display element is illuminated with the first wavelength, and outer areas of the display element are illuminated with the second wavelength.

[0198] Fig. 6 shows a schematic representation of a further arrangement for the optical processing of the starting material 3 in the receiving vessel 1. Fig. 7 shows a schematic partial representation of the arrangement. Fig. 6 .

[0199] A light section 60 is generated in a horizontal plane 61 by means of a laser beam 62, which enters from above into a dip tube 63 that is optically transparent to the laser beam 62 and is deflected into the receiving vessel 1 containing the starting material 3 by means of a motor-driven, rotating mirror 64. The light section 60 of the first wavelength is created by rotation. Projector light 66 of the second wavelength is shone through a bottom 65 of the receiving vessel 1 to sharply image a projector image 67 in the horizontal plane 61 of the light section 60.

[0200] The immersion tube 63 is closed at the bottom. The motor-driven, rotating mirror 64 and the laser beam path 62 are separated from the starting material 3 in the receiving vessel 1. For processing the starting material 3, the immersion tube 63 is moved up or down, thereby shifting the horizontal plane of the light section 60 upwards or downwards.

[0201] Fig. 8 shows a schematic representation of a further arrangement for the optical processing of the starting material 3 in the receiving vessel 1 in a top view ( Fig. 8a ) and a side view ( Fig. 8b The laser beam emanating from the laser 80 is directed by a galvanometer scanner 81 through a lens 82 onto a mirror ring 83, thereby creating a circular light section of the first wavelength. The light of the second wavelength is provided by a projector unit 84 and directed orthogonally to the light section into the receiving vessel 1 by means of a mirror 85.

[0202] Further aspects of the process for optically processing the starting material 3 are explained below.

[0203] The local polymerization of the starting material 3, mediated by light excitation of the photoinitiators, occurs via a sequential process in which processing takes place layer by layer in the free volume within the receiving vessel 1. First, the desired three-dimensional object is sliced ​​into individual layer images with a defined grid spacing. By superimposing the light section from the light source 5 and the respective cross-sectional image from the projector 7, the dual-color photoinitiators are excited from their ground state A to their active form C, which initiates the local polymerization of the starting material 3.After the exposure sequence for the current layer (layer subvolume) has elapsed, the light excitation is shifted by moving the receiving vessel 1 and / or the light section and the projector 7 together, and the exposure of an adjacent or any other layer (another layer subvolume) is performed. The translation of the projection arrangement or the receiving vessel 1, which can be realized, for example, by means of suitable stepper motors, can optionally be located below the waist diameter of the light section in order to increase the resolution in the direction of movement.

[0204] For the timing of an exposure sequence for each layer volume, there are various options that are used depending on the starting material and the properties of the dual-color photoinitiators used: Variant (1): Simultaneous activation of both light sources (λ₁, λ₂, and optionally λ₃) with defined, potentially different intensities for a predetermined exposure time. After simultaneous deactivation, the system begins translation to the next layer. Variant (2): The first light source 5 (light section generator) and the projector 7 are operated in pulsed mode. The number, duration, and intensity of the pulses, as well as the time offset between the starting edges of both pulses, can be freely adjusted within a defined exposure time per layer volume. When using multiple pulses within the processing of a layer volume, a different image from the projector 7 can be assigned to each pulse. After the exposure time, translation to the next layer volume takes place.Variant (3): The first light source 5 (light section generator) remains switched on at all times, while the projector image is switched to the next layer after a defined exposure time as the arrangement is translated. Variant (4): Physically possible combinations of variants (1), (2) and (3).

[0205] The volumetric process presented here generates the desired three-dimensional object by polymerizing the starting material 3 layer by layer within the working volume 2, while leaving the basic structure of the starting material 3 unchanged. This is an advantage over processes that can only process the starting material in separate layers. Due to the layer-by-layer exposure, the process is inherently faster than polymerizing the starting material point by point.

[0206] Due to the widening of the light section, a larger area of ​​the working volume 2 can be processed simultaneously and therefore faster, but this results in a loss of resolution.

[0207] The generation of the light section using light source 5 results in a coupling between the minimum waist diameter and the divergence of the beam, leading to a widening of the light beam towards the edge of the volume. This allows either a homogeneous, medium resolution to be generated along the light section or a higher resolution in the waist region with a greater drop-off towards the edges.

[0208] Since earlier processing of layers that are further away from projector 7 is possible in the time sequence, a possible influence on the light propagation of the projector image (light of the second wavelength) by already cured layers is avoided.

[0209] Due to the shift in the light section, each layer volume is processed only once and thus receives a defined energy dose. This effectively reduces the polymerization of unwanted areas when using non-ideal dual-color photoinitiators.

[0210] If the kinetics of the reactions of the photoinitiator molecules and the starting material 3 triggered by light irradiation are sufficiently known, the targeted timing of the light pulses relative to each other and a suitable selection of the intensities of both wavelengths allow for a higher discrimination between desired and undesired polymerization in the working volume 2. This reduces artifacts and a degradation of the resolution for non-ideal dual-color photoinitiators.

[0211] The features disclosed in the foregoing description, the claims and the drawing can be important for the realization of the various embodiments, both individually and in any combination.

[0212] Individual features of the invention are illustrated again by way of example in the following aspects: 1. A method for producing an optical element by processing an optically reactive material, comprising: providing a starting material (3) which is optically reactive and fills a working volume (2); optically processing the starting material (3) in the working volume (2) by irradiating it with light of a first wavelength and light of a second wavelength, which differs from the first wavelength, wherein at least one material property of the starting material is changed by means of the optical processing, and wherein the optical processing comprises: irradiating a first layer subvolume of the working volume (2) filled with the starting material (3) with the light of the first wavelength; irradiating the first layer subvolume of the working volume (2) with the light of the second wavelength,wherein the light of the second wavelength is projected into the working volume (2); irradiation of a second layer subvolume of the working volume (2) filled with the starting material (3), which is different from the first layer subvolume, with the light of the first wavelength; irradiation of the second layer subvolume of the working volume (2) with the light of the second wavelength, wherein the light of the second wavelength is projected into the working volume (2); and repetition of the preceding steps for layer-by-layer optical processing of the starting material (3) in the working volume (2) until a volume of the starting material (3) to be processed, which wholly or partially encompasses the working volume (2), has been optically processed, and a green compact has been formed from the starting material (3); and further processing of the green compact so that an optical element is formed from the green compact, at least partially, in particular completely. 2. Method according to aspect 1,wherein the further processing of the green compact comprises at least one of the following steps: removal of the green compact from the starting material; treatment of the green compact with a solvent and / or a monomer; drying of the washed green compact; and photochemical and / or thermal post-curing of the green compact. 3. Process according to aspect 2, wherein the solvent and / or the monomer comprises a thermal initiator and / or a further photoinitiator, which preferably reacts to only one wavelength. 4. Process according to at least one of the preceding aspects, wherein the further processing of the green compact comprises at least one of the following steps: annealing of the green compact, grinding of the green compact, polishing of the green compact, and coating of the green compact. 5. Process according to at least one of the preceding aspects,wherein the light of the first wavelength and the light of the second wavelength are simultaneously illuminated together into the first or the second layer volume for at least a temporal overlap period, wherein preferably the light of the first wavelength is illuminated onto the starting material (3) in the working volume (2) along a first direction of illumination and the light of the second wavelength along a second direction of illumination, which is perpendicular to the first direction of illumination. 6. Method according to at least one of the preceding aspects, wherein a polychrome multiphoton polymerization is triggered in the starting material (3) by means of optical processing, which causes the change of at least one material property of the starting material (3). 7. Method according to at least one of the preceding aspects, wherein the starting material comprises a transparent organic polymer and / or an inorganic / organic polymer composite.which preferably hardens by optical processing. 8. Method according to at least one of the preceding aspects, wherein the starting material has a viscosity of 10⁻² mPa·s to 10⁷ mPa·s and / or a yield strength of at least 0.1 Pa. 9. Method according to at least one of the preceding aspects, wherein the formation of the optical element comprises the formation of at least one optical lens, an imaging lens, an intraocular lens, a lens array, a diffuser, a prism, an optical grating, a diffractive optical element, and an optical waveguide. 10. Method according to at least one of the preceding aspects, wherein at least one functional element is provided in the starting material (3) and the optical element is formed at least partially adjacent to the at least one functional element. 11. Method according to aspect 10.wherein the at least one functional element comprises at least one of the following elements: an actuator element, a sensor element, an energy source element, a display, a lens holder, and at least one other prefabricated optical element. 12. Method according to aspect 10 or , 11,wherein the at least one functional element has a refractive index that differs from a base material refractive index by no more than 3%. 13. Method according to at least one of aspects 10 to 12, wherein, during optical processing, the base material around the at least one functional element is irradiated with first-wavelength light and second-wavelength light from at least two sides. 14. Method according to at least one of the preceding aspects, wherein the irradiation with first-wavelength light and / or second-wavelength light is carried out using multiple light sources (5) such that the light is irradiated into layer subvolumes which are at least partially superimposed. 15. Method according to at least one of the preceding aspects, wherein it is determined whether the first or the second layer subvolume is irradiated with the first wavelength.and a projection device (7) for projecting the light of the second wavelength into the working volume is controlled as a function of this, to project the light of the second wavelength into the first or into the second layer subvolume, in particular in a specific intensity distribution. 16. Method according to at least one of the preceding aspects, wherein the light of the first wavelength and the light of the second wavelength are simultaneously and jointly illuminated into the first or the second layer subvolume for at least a temporal overlap period. 17. Method according to at least one of the preceding aspects, wherein the first and the second layer subvolume in the working volume (2) form adjacent layer subvolumes of the starting material (3), optionally wherein the first and the second layer subvolume are formed according to one of the following configurations of subvolumes: overlapping at the edges,abutting each other at the edges and spaced apart from each other at the edges. 18. Method according to at least one of the preceding aspects, wherein the light of the first wavelength is emitted by means of several light generators for the generation of a light section, which shine into the working volume from different sides of a working vessel containing the working volume and generate the light section into which the projection takes place by means of the superposition of partial beams. 19. Method according to at least one of the preceding aspects, wherein the light of the first wavelength is emitted by means of four light generators for the generation of a light section, which, in particular in pairs opposite each other, shine into the working volume from different sides of a working vessel containing the working volume and generate the light section by means of the superposition of partial beams.in which the projection takes place. 20. Method according to at least one of the preceding aspects, wherein at least two differently oriented light sections are generated, in particular at least two differently oriented light sections which overlap in the working volume. 21. Method according to at least one of the preceding aspects, wherein, to generate a light section in the working volume, the light of the first wavelength is shone into the working volume with a rotational movement. 22. Method according to at least one of the preceding aspects, wherein the optical processing of the starting material (3) is observed with the aid of a light detector (8a; 8b), in particular a camera or a photodetector. 23. Method according to at least one of the preceding aspects, wherein a polychrome multiphoton polymerization is triggered in the starting material (3) by means of the optical processing.which causes the change of at least one material property of the starting material (3). 24. Method according to at least one of the preceding aspects, wherein the light of the first wavelength is first irradiated into the first layer volume and then into the second layer volume with a distribution that is substantially homogeneous or non-homogeneous with respect to at least one of the following light parameters: light intensity and light color. 25. Method according to at least one of the preceding aspects, wherein a light section is generated in the working volume (2), in particular a light section of the light of the first wavelength, and during the movement of the light section through the working volume (2) a focus correction, in particular a focus correction of the light of the second wavelength, is continuously carried out. 26. Method according to at least one of the preceding aspects,wherein the starting material is subjected to at least one process for removing impurities, in particular particulate impurities, prior to irradiation, wherein the process in particular comprises filtering the starting material by means of a filter device. 27. Method according to at least one of the preceding aspects, wherein the further processing of the green compact, such that an optical element is at least partially, in particular completely, formed from the green compact, in particular the post-curing of the green compact, is carried out under a protective gas atmosphere, in particular an argon, carbon dioxide or nitrogen atmosphere. 28. Method according to at least one of the preceding aspects, wherein the further processing of the green compact comprises photochemical post-curing of the green compact by means of at least one additional photoinitiator, wherein the additional photoinitiator is configured29. A photochemical reaction causing photochemical post-curing of the green compact at a wavelength different from the first and second wavelengths. 28. A process according to aspect 28, wherein the additional photoinitiator is an alpha-diketone, in particular camphorquinone, or contains at least an alpha-diketone, in particular camphorquinone. 30. A process according to aspect 28 or 29, wherein the additional photoinitiator is irradiated with a wavelength that lies between the first and second wavelengths. 31. A process according to at least one of the preceding aspects, wherein the further processing of the green compact includes treating the green compact with a solvent and / or a monomer, in particular for washing the green compact, wherein a solvent and / or a monomer with a molar mass greater than or equal to 200 g / mol is used. 32. A process according to at least one of the preceding aspects,further processing of the green compact includes treating the green compact with a solvent and / or a monomer, in particular for washing the green compact, wherein a highly volatile solvent and / or a highly volatile monomer is used. 33. A process according to at least one of the preceding aspects, wherein a starting material is used which is free of inorganic and / or organic particles, in particular free of inorganic and / or organic particles with a diameter greater than 50 µm. 34. A process according to at least one of the preceding aspects, wherein a starting material is used which contains exclusively organic components. 35. A process according to at least one of the preceding aspects, wherein a starting material is used which is free of organic polymers. 36. A process according to at least one of the preceding aspects,wherein the optical element to be produced has a planar geometric shape having a principal plane of extension, wherein the orientation of the optical element is chosen to be perpendicular, in particular perpendicular, to the principal plane of extension. 37. Method according to at least one of the preceding aspects, wherein the first wavelength is less than or equal to 400 nm, in particular less than or equal to 375 nm, and / or wherein the second wavelength is greater than 400 nm, preferably greater than 500 nm. 38. Method according to at least one of the preceding aspects, wherein the starting material and / or the photoinitiator and / or a co-initiator is free of amine compounds or contains no more than 10 wt.% of one or more amine compounds. 39. Method according to at least one of the preceding aspects, wherein at least one first irradiation device is used which is configured to irradiate light of the first wavelength into the working volume (2).to generate at least one first light projection in the working volume, wherein the at least one first light projection comprises several light rays passing through the working volume (2) in at least one plane of light; and at least one light modulation device is used, which is associated with the at least one first irradiation device, wherein the at least one light modulation device is configured to modulate the spatial direction of extension of two or more of the several rays in the at least one plane of light such that the two or more light rays extend in a non-parallel arrangement relative to each other. 40. Method according to aspect 39, wherein the at least one light modulation device comprises one or more optical elements, each optical element being configured to change the original spatial direction of extension of an incident light ray,to generate a light beam that has a different spatial direction of extension relative to the original spatial direction of extension. 41. Method according to aspect 40, wherein the optical elements are configured as or comprise optical lenses, in particular microlenses, and / or optical diffuser elements, in particular elliptical diffuser elements. 42. Method according to at least one of the preceding aspects, wherein at least one measure is taken to modify the optical properties of the green body, wherein the at least one measure preferably comprises modifying the optical properties of the green body to reduce the absorption properties of the green body for at least one wavelength in a wavelength range between 300 nm and 2000 nm, in particular between 350 nm and 900 nm.and / or leads to an increase in the transmittance properties of the green compact for at least one wavelength in the wavelength range between 300 nm and 2000 nm, in particular in the wavelength range between 350 nm and 900 nm, and especially in the wavelength range between 400 nm and 800 nm. 43. Method according to aspect 42, wherein the at least one measure comprises a thermal treatment of the green compact and / or an optical treatment of the green compact, in particular by irradiating the green compact with electromagnetic radiation, and / or a chemical treatment of the green compact. 44. Device for processing an optically reactive material for producing an optical element, comprising: a working volume (2) configured to receive a starting material (3) that is optically reactive and partially or completely fills the working volume (2); a lighting device configured toto provide light of a first wavelength and light of a second wavelength for illumination onto the working volume (2) containing the starting material (3); and wherein the illumination device is configured to optically process the starting material (3) in the working volume (2) as follows: irradiating a first layer subvolume of the working volume (2), which is partially or completely filled with the starting material (3), with light of the first wavelength; irradiating the first layer subvolume of the working volume (2) with light of the second wavelength; irradiating a second layer subvolume of the working volume (2), which is different from the first layer subvolume.with the light of the first wavelength; irradiating the second layer volume of the working volume (2) with the light of the second wavelength; and repeating the preceding steps for layer-by-layer optical processing of the starting material (3) in the working volume (2) until a volume of the starting material (3) to be processed, which wholly or partially encompasses the working volume (2), has been optically processed. 45. Device according to aspect 44, wherein the illumination device comprises at least one of the following elements: a Powell lens or a polygon mirror or a galvo scanner, and / or wherein the illumination device comprises: a laser or an LED or a thermal light source. 46. Device according to aspect 44 or 45, wherein the illumination device is configured to allow earlier processing of layers that are further away from a source of light of the second wavelength. 47. Optical element,produced using a process according to at least one of the preceding aspects.

Claims

1. Method for producing an optical element, wherein an optically reactive material in a working volume is optically processed multidimensionally or spatially with light of a first and a second wavelength, such that by means of irradiating the light of the first and second wavelength, or optionally of light of one or more further wavelengths, at least one material property of the optically reactive material is changed and an optical element is obtained by means of post-processing.

2. The method of claim 1, wherein the method is a volumetric printing process which enables the continuous production of isotropic objects.

3. Method according to claim 1 or 2, wherein the optical element is formed at least partially adjacent to at least one functional element.

4. Method according to one of the preceding claims, wherein the optical element is formed around at least one functional element, preferably such that the optical element formed at least partially, and in particular completely, encloses the at least one functional element.

5. A method according to claim 3 or 4, wherein the at least one functional element comprises at least one of the following elements: an actuator element, a sensor element, an energy source element (for providing electrical energy, for example, a solar cell), a display, a lens holder (lens mount), and a further prefabricated optical element. Additionally or alternatively, the at least one functional element may comprise at least one optical component, in particular at least one of one or more apertures and optical filters.

6. Method according to any of the preceding claims, wherein the at least one functional element is a lens, a lens array, an optical grating, a diffractive optical element or an optical waveguide, wherein, optionally, the optical element is formed bound to an optical fiber and / or a light source.

7. Device for processing an optically reactive material for the production of an optical element, comprising: - a working volume configured to receive an optically reactive material which is optically reactive and partially or completely fills the working volume; - an illumination device configured to provide light of a first wavelength and light of a second wavelength for illumination onto the working volume containing the optically reactive material, wherein the illumination device is configured to optically process the optically reactive material in the working volume as follows: irradiating a first layer subvolume of the working volume partially or completely filled with the optically reactive material with light of the first wavelength;Irradiating the first layer subvolume of the working volume with light of a second wavelength; irradiating a second layer subvolume of the working volume, which differs from the first layer subvolume, with light of a first wavelength; irradiating the second layer subvolume of the working volume with light of a second wavelength; and repeating the preceding steps for layer-by-layer optical processing of the optically reactive material in the working volume until a volume of the optically reactive material to be processed, which wholly or partially encompasses the working volume, is optically processed, in particular by forming a corresponding green compact;- a control device which is configured to control the lighting device so that the layer volumes of the optically reactive material are processed layer by layer one after the other, wherein the control device is configured to change the external shape of projections of the light of the second wavelength for different layer volumes depending on an optical element to be produced.; 8. Optical element produced by a process comprising: i) processing an optically reactive material in a working volume multidimensionally or spatially optically with light of a first and a second wavelength such that, by means of irradiating the light of the first and second wavelength, or optionally of light of one or more further wavelengths, at least one material property of the optically reactive material is changed; ii) post-processing of the object produced in i) to form the optical element.

9. Optical element according to claim 8, wherein it is processed by laser processing and / or mechanical processing.

10. Optical element according to claim 8 or 9, wherein it is formed at least partially in contact with at least one functional element.

11. Optical element according to one of claims 8 to 10, wherein it is designed to at least partially enclose at least one functional element.

12. Optically reactive material for producing an optical element in a process, wherein an optically reactive material in a working volume is optically processed multidimensionally or spatially with light of a first and a second wavelength, such that by means of irradiating the light of the first and second wavelength, or optionally of light of one or more further wavelengths, at least one material property of the optically reactive material is changed and an optical element is obtained by means of post-processing.

13. Optically reactive material according to claim 12, comprising one or more of the following components: oligomer (for example, acrylate, methacrylate, epoxy, vinyl, allyl, organopolysiloxanes, terminally functionalized polysiloxanes), functionalized and non-functionalized nanoparticles, monomer (for example, acrylate, methacrylate, epoxy, vinyl, allyl), crosslinker (for example, multifunctional monomers, multifunctional thiols), dual-color photoinitiator, co-initiator, inhibitor, sensitizer, defoamer, post-processing additive (for example, additional photoinitiator and / or thermal initiator), solvent, additive, in particular a rheology control additive (rheology modifier), especially of the optically reactive material, a surface tension reduction additive, especially of the optically reactive material, an additive for influencing the optical properties, for example, to adjust or increase the transparency orAdjustment of the refractive index, in particular of the optically reactive material or optical element.

14. Optically reactive material according to claim 12 or 13, wherein it has a yield strength greater than or equal to 0.1 Pa, in particular 0.2 Pa, further in particular 0.3 Pa, further in particular 0.4 Pa, further in particular 0.5 Pa, further in particular 0.6 Pa, further in particular 0.75 Pa, further in particular 1 Pa.

15. Use of an optically reactive material for the production of an optical element in a process, wherein the optically reactive material is processed multidimensionally or spatially in a working volume with light of a first and a second wavelength, such that by means of irradiation with light of the first and second wavelength, or optionally with light of one or more further wavelengths, at least one material property of the optically reactive material is changed and an optical element is obtained by means of post-processing.

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